I'm 12 and I want to know how much should i be lifting to help my biceps.
Very light as your still young...your bones are still growing so are soft and what you do now will affect you when your older! Stunted growth, deformed Skeltal structure etc...
That out the way I remember when I was around that age maybe a little younger and watching Rocky films hyped me up so I used to put bricks in a milk crate (glass pints back then) tied to a rope over a beam in the shed and lift adding extra bricks...fun days wish I kept it up!
So start with low weights I would really go over say 10kg till your older a good app is Jefit which shows muscle groups you can work on and 100s of excersises that you can do!
Good luck and stay safe little warrior!