This can also apply to pull ups. I can do 22 dead hang chin ups and 5 one armed chin ups. So I know them well.
1. I cannot do 1 chin up/1 pull up
First thing you do are these two movements:
The Australian Pull-up.
The “Negative” Chin Up. Where you put a box or something under the bar and hang on to it in the flexed arm position then lower yourself down on the box.
Assisted chin ups can also help you work your way up. You can also do them band-assisted or on your knees with some box under you.
You can also hang from the bar to increase your grip so your able to do 1.
2. Losing Weight
Losing weight can help increase the rep count. You have less weight to lift up ergo you can do more reps.
3. Do more chin ups
Doing alot of chin ups over the course of 24 hours will increase the number of reps you can do.
4. Chin up/Pull up Programs