Workout suggestions?

So, I'm new here...yay and I was wondering where would be a good place to start.

First off, I'm not exactly looking to lose weight, more so to gain muscle. I am a 5ft 3in, 120lbs teenager and quite comfortable with my body. However, I am quite noodle armed and this doesn't sit well with me. Overall, I'd like to become more toned and maybe start working towards the legendary six pack.

Second, while the workout plans look nice, I'd like to be sure that this is something I can and will stick to. So, for now at least, I'd like to stick to the free videos.

So, any suggestions as to where I should start? Any advice is appreciated!