I started doing pull-ups for the first time last year (or maybe it was earlier this year). The way I trained up to them was by following a tip from a friend: reverse pull-ups. I’d start up on a stool, grab the bar, and then slowly lower myself down with my arms. Once I built myself up to 3 sets of 4 reps every other day, I’d periodically try to do a full pull-up. And one day I found I could do them no problem.
This wasn’t a quick process though. I think it probably took two months or maybe three.