While their FAQ seemed great to me, I'm someone already familiar with why this is important and generally how to do it. I could see it being overwhelming to someone just considering the idea. https://forwardemail.net/en/faq#table-of-contents
Forward Email does a pretty good job with onboarding new users, in my opinion. Yes, some technical know-how is expected (you do need to know how to update DNS records for your domain, for example) but they give you step-by-step instructions both for setting up the MX and TXT records in DNS and for configuring your Google Mail account (or possible others, I didn't check) to allow sending email using your new address. I found it simpler to set up the forwarding itself than to go around to all my accounts and update the email addresses; that part is still a work in progress.
[0] https://medium.com/hackernoon/when-and-how-to-use-2019s-best...