I'll list off the things that are probably needed, well, I am 16 years old, I'm 5'10 in height, I weigh 137 pounds. I have never worked out before, so I pretty much lift dumbbells horribly - about 20 pounds. I have a pull-up bar which is able to attach to my door, so I use that often now.
I'll go from that, but my question is, how can I increase body mass, build my body muscles, and keep fit?
I'll start from that.