1. Start today by doing literally anything active.
2. Do it again tomorrow.
3. Repeat.
There is no magic. Once you’ve got a habit of showing up, you can worry about exactly which fitness routine to use. Most programs get repetitive after 6-8 weeks anyway, so you need a foundation of a stable habit to fall back on when switching routines or burning out on one.
The secret is to show up. Every day. Just keep stacking those good days.
(This applies to a lot more than just fitness, btw)
(It’s also much easier said than done)