No worries, first set the speakers up in your room how you want them then position the sub. After this time run all the cables back to the sub and use the letter to find out which goes where, looking at my 2.1`s now i can see this on the back of the sub + L - meaning thats the left speaker and all you have to do from hear is match red with red and black with black very easy stuff but actually harder to explain then you would think.
all the best, and enjoy your speakers.