How do I gain weight/bulk up when I have high cholesterol?

I m 25 years old. I m pretty skinny and play soccer. I was told that my cholesterol was high by my doctor and his advice was just to change my diet. I m assuming my cholesterol rose to high levels because of a few things: skipped breakfast, ate a lot of fast food everyday, stopped playing soccer and exercising because of a toe injury and hedetitary.

I was at 150 lb have dropped to 137 lb because of my diet change. I did stop eating fast food and started eating a lot better. I was just wondering how I can bulk up since I am already skinny. I will be going to the gym, but how should my diet be? Still need to eat well for my cholesterol.