Take lessons. It doesn’t need to be weekly or even steady like when you were little. There are beginner piano lesson books tailored to adults, and having a teacher who can walk you through it, discuss your interests and goals, and answer your questions is worth the money, even if you meet once a month or just schedule per-basis when you feel ready to meet again. A local music shop can put you in touch with a teacher that knows rock.
And don’t give up when it’s hard. It’s hard to learn new skills. Trust that your brain accomplishing work in the background even when you feel like you’re not making progress, which will happen sometimes. One day you’ll wake up and find that the impossible chord progression you’ve been stuck on for weeks is a little bit easier all of the sudden, then it’s on to the next milestone.