Be able to do a pull-up

I’ve never been able to do a pull-up. Right now, at around 224 lbs, I’m waaaay too heavy to pull myself up. But, between my new eating plan and getting regular exercise now, I want to be able to do this. Once a week I get to track my progress at the gym :o)

Ok, I know why. I’m 20 pounds over weight, a women and have little upper body strength (good legs though). My immediate family (husband and 2 step kids) have contests to see who can do the most. I can’t even do one!!
I think I know how to get there:
1. Lose 20 pounds
2. Build shoulder and back muscles

Unfortunately I have been thinking about this for over 3 years. I’m no closer to it. Bummer.