Cool, so you actually look pretty good in that after photo. You're definitely in a great place to start.
The thing you'll need to be ok with, is that 99% of the advice online is written with adults in mind, and so isn't perfectly applicable to you. You'll be reading a lot of stuff about high intensity training, intensity techniques, all sorts of ways to really brutalise yourself.
While obviously you should be training hard, you need to accept that while your body is growing and developing you don't want to be smashing yourself into bits deadlifting heavy singles and shit like that.
@Chris_Colucci wrote an amazing article on the subject
I understand it's a hard sell at first as bodyweight stuff is kinda boring - but check out phase II.
You also need to pay particular attention to the dietary guidelines. People always recommend asinine things like eat 5000 calories, or bulk up until you can't see your abs or whatever. Bullshit. At the age you are you need to think about ingraining habits of being as healthy as possible. Don't think about things like calories or whatever; just eat to nourish your body as best you can. If you do, you'll be muscular and lean without even trying.