Re: I cannot even do 1 pull up. What muscles should I train to improve this?
Build your self up to it from Lat pull downs.
Some gyms even have an assist counter weight on their pull up bar!
If you are at home try negative and partial rep pull ups, climb trees etc
Training muscles (bicep lats etc) is no where near as effecient as attempting the exact or simlar movement. So dont waste your time.
You may have to loose the weight before you can do a single pull up, the heavier you are the lower your strength to weight ratio when it gets to high body weights!