How can I learn a piece that I can't play?
One note at a time.
If you are "talented", as questioning in your adjacent thread, you'll hear the note, and first find it's location on the neck. Second, you'll decide more intricacies, such as, the timbre, attack and energy behind the note, and intuit what approach to striking the note you choose.
After a while, your intuitive nature will help you to be able to do so much more quickly, with your interest/enthusiasm at the throttle.
As a young teen, I ate every freakin' note I heard, and either had a clue immediately how they were producing said notes, or quickly grabbed the instrument and took educated guesses.
Was I right every time? Absolutely not.
Did I learn and become proficient in a hurry? Of course. Even a few wrong guesses get you further down the road towards proficiency.
40 years later: Still doin' it, 'cause I love the crap out of music, and especially playing bass.
Still learning.
It's a life long process. Settle in. So many notes, so many bands, so much growth coming your way. It's gonna be a blast!
You've made a good decision to begin playing, which shows self-motivation, discipline and drive.
That is where real progress lives.