Been reading and trying to apply trp to my life for a while now, started college (uk) 2 months ago and girls have started noticing me.

I normally run and this means my arms are twigs and there's no muscle, I wanna join a gym but I don't wanna go in to hard and injure myself. I know there's plenty of posts about this but they might not apply to someone my age.

What kind of exercises should I do

•How many times a week?

•How many reps?

•What to eat to put on weight?

Thanks for the help anyone.