RE: First timer, need help getting all the parts together
ESC Controls the Current from the Battery, to the Motor..
Choosing an ESC, You need to make sure that it has a power handling range to suite your motor..
In General, Staying 2 Turns above the ESC's motor rating is a good rule of thumb for ESC life.
So, If You buy a 15T limit ESC, then you can run motors down to a 17tX2 safely.
If You use a 12x2T Motor on a 20T ESC then you can Expect a Smoke Show in no time at all..