So I should obviously move bxc3. What should I be looking ahead for?

I would try to expand the centre with e4 after some preparation and use my 2bishops to conquer the centeer

bxc3 is correct.

A note to forum moderators. Would it not be a good idea to have forum rules in their own separate board so that they are easy to find? It wasn't immediately obvious (at least to me) that they would be under the chess.com community board.

Also, clarification in the rules, as to whether seeking assistance in an unrated yet currently active game is allowed.

Thanks for telling me I'am brand new and did not realise it. Yes it is unrated. I am mostly just intrested in theory not specifics but I will delete my question. 

Without seeing the question, I can deduce from the second comment and the title it must be about the Nimzo-Indian, something like this :

... in which case, usually, White's plan is to attack the Black king, while Black's is to attack the c4 pawn hoping to force White to trade off one of his bishops. (no specific moves while it's ongoing...)

Thanks for the help. 

How does black attack c4 pawn?in that position,or should that have been the objective before B moved to b4?

After checking the game in progress, and its completely different position, I can answer as Black won't resort to this plan...

In the position I give (Saemisch variation of the Nimzo-Indian), after 5.bxc3, Black's next moves are almost always ...b6, ...Nc6 and ...Ba6 (in either order). White must then defend the c4 pawn with the queen, as Nf3 (with the idea Nd2) would stop his idea to expand in the center with f3 and e4 (5.bxc3 Nc6 6.f3 is the most played move). Then, against Bd3 and Qe2 Black can play ...Na5-b3 to trade the pair of bishops, or (better IMHO) play to place his pawns on dark squares to make the bishop pair inefficient ; and against Qh4 bring the queen to c6 to trade the queens (reducing the attacking power of White who controls the center).

I can only recommend Reinaldo Vera's Chess Explained: The Nimzo-Indian if you want to study better this opening ; I found it not only instructive and complete, but also reader-friendly, which is by far not the case of all the Chess explained books.