The earlier you begin, the "easier" it comes, I think.
Penis Enlargement takes time though, regardless of age. But being just 16 or in your teens, the body is highly adaptive and usually able to push further. As we progress and get older, some things diminish.
I wouldn't say 16 is too early to begin Penis Enlargement. But always start with a [words=http://www.mattersofsize.com/forum/penis-enlargement-newbie-forum/1597-dlds-first-routine-i-gained-2-inches-with-this-routine-full-tutorial.html]newbie routine[/words], go slow, go long. Going too hard too fast can lead to overtraining and cause difficulties in gaining.
Going commando or wearing loose boxers is one of the easiest starting points! I'm sure there are decent boxer shorts available where you live. Maybe even take a one size larger than your regular size, see what suits you the best. But truly, let it hang free.
Stick with the program, which would be the newbie program for now. Concistency brings results. Don't beat yourself if you miss a day or so. Especially don't go for harder session if you happen to miss a session.
We're all inviduals (I must have repeated this so many times), so remember to listen to your body. Dull ache / soreness is alright. Good erection quality is also a great signal of things going smoothly or too rough.
Take care of your diet, remember to consume water.
All the best!