If you are younger than 10-12 years I'd say you are too young, but once you are highschool age, you're fine for lifting and not having to worry about getting a stunted height.
If you want to be an athlete first of all, your arms are not super important, in fact, your biceps are one of the least important muscles for being good in sports. I assume you are thinking you need defined biceps and pecs due to the stereotypical strong guy look.
If you do start a lifting routine, I would reccomend the following.
Monday / Wednesday / Friday : Upper Body
Bench Press (Pectorals (Chest))
Dips (Tricep/ Pectorals / Lat Dorsi (Mostly chest, but also some back of upper arm and upper back)
Bent Over Back Rows (Latissimus dorsi (Upper Back))
Curls (Biceps (top of upper arm))
Skull Crushers (Triceps (back of upper arm))
Militry Press (Deltoids (Shoulders))
Ab work, (there are about ten thousand different ab work outs, just google it and find one you like)
Tues / Thurs / Sat: Lower Body
Squats (Quadriceps (front of upper leg))
Gluteal work (butt)
Calf Raises (gastrocnemius (back of lower leg))
Agility work
That is what I can come up with off the top of my head right now, and if you have any questions about why or how to do any of the above, post, and I'll let you know.