Step 2. Optimize software. Your brain is a neural network that needs reinforcement learning to learn anything. Be open minded, adopt a mental framework of picking up new things and doing them, iteratively figuring things out. You need to leverage the hedonistic aspects of your human brain - i.e you need to get some "reward" from doing activities that improve you knowledge, which mean you have to tailor your activities towards that. For example, if you want to get good at circuits, you should aim to build widgets that improve your life somehow, instead of random hobby projects.
Thats pretty much it. The issue that most people have is you often have to have the first part of step 2 to do step 1, and if you don't do step 1, you lack the capability to execute step 2. How to break the loop is different for every person, but psychedelics seem to be of good use.
According to current psychological evidence you cannot become more intelligent. Intelligence is fixed. You can, however, study with great focus and intensity with a goal of increasing your intelligence, but the results are tiny and extremely temporary.
Instead of becoming more intelligent you can always become more educated. The results of increased education vary significantly by person and may result in near-permanent contributions. The goals of increased education are increased skills, increased decision making capacity, and increased risk appreciation.
That's not what it feels like.... that's what it feels like after you learn you were wrong. There's no difference in feeling between being right or wrong. So, if you want to be right more often (a proxy for being "smarter), I suggest the following.
Write down predictions somewhere, along with your view of the world, things you're worried about, etc. Keep it private, but be as descriptive as you can to yourself, as time goes on, you can then retrospectively see where your biases and fears have distorted your thinking, and find clues to the things you were right about, but too afraid to follow up on. Over time, you should gain both perspective and wisdom, and perhaps a bit of "smarter" as well.
By trying to obtain a grander perspective and awareness of the scale and scope of the universe, one sees many limitations of our own species :)
Perhaps, one such limitation is an inability to define what really is meant by "intelligence".
Relevant example - inventing the atomic bomb (result of intelligence), using the atomic bomb (result of same "intelligence"?). There are many such examples, showcasing how confused/irrational members of the species can get.
Maybe it is just wiser to sidestep the question altogether, and ask a better question, something that can be answered.
In my opinion, the problem stems from trying to get an extremely generic definition capturing performance in all sorts of disparate behaviors and activities.
What the top performers in all fields have in common is that they made a decision at some point in their lives to truly go all in on being the best at a particular thing, and that takes sacrifices that you probably don't want to make, and there's nothing wrong with that. There is no shame in not being a high performer and just being generally okay at everything.
This is mostly ignoring the true outliers with very high IQs, but that is such a huge anomaly statistically that there is no use even discussing it. It is not the norm among even the most successful entrepreneurs or fortune 500 CEOs or endowed chairs of Computer Science.
With having knowledge in different domains, one should learn to interconnect Domains in a chain-of-thought.
This isn't easy. But can be trained. Just like with different languages. You may be able to speak several languages fluently. But to speak with the grammer of the first, using the words of the second and "thinking" in third - fluently - isn't as easy, if the third isn't your mother language. But this can be trained. I needed like 2 months with each day talking am the phone to reach that ability. So. I'm smart now :)
The same applies to technical knowledge, that needs to be interconnected with economic knowledge. One's need to train train train.
The application of knowledge gets trickier because there is almost always no "right answer". Everything is a decision, a choice. There may even be conflicting but contextually correct ways to process the same decision - i.e. Early bird gets the worm vs second mouse gets the cheese.
One thing is knowledge. Other thing is to get that knowledge transferred into, f.e. movement for use of a machine.
Like a real example, the Chinese. They're developing such a phenomenal ability to visually memorize things since their childhood on. As students, whole books are memorized. But ask them to utilize that knowledge, they just can't. They haven't learned how to utilize knowledge practically, in contrast to the western worlds approach to school. But we here have a bad visual memorization.
So you take a Chinese Teen, who finished the college purely the Chinese way and put him in one of western world's universities. You'll get an absolute killer.
Gaining knowledge the western way, memorize in Chinese visual way.
The decision you talking about needs to be done in every situation of a daily life. The quality of decision depends on the knowledge. The knowledge by itself needs to be broad. You need to be able to access each part of the broad knowledge individually and bring everything in relation. That's only can be done with training. And the use case defines the knowledge needed
"Do I buy a desktop PC or a very expensive laptop?" vs. "Should I buy Rheinmetall stock for profit or real estate" vs. "The law passed last week is damaging my core business. Pivot? Where to?"
As a very broad brush generalisation, you become smart by learning from those who are smarter than you in your chosen field. You could accomplish that by reading, seriously studying, being mentored and most critically practising your "craft".
If you simply just learn a huge pile of facts and are able to regurgitate them at will, then most people will think you are a "smart alec", which is probably not what you want to be known as.
But that should be a compliment in one's eyes. If the not so smart ones think your arrogant-> achievement unlocked
Won't make you smarter, but will bring out the smarts you were born with.