Why not take a program like Nagaskaki and start off with the lowest rated characters and work your way up?
Stockfish 6 to improve

I'm trying to beat Stockfisk lvl 6 as a way of improvement - is this a good idea?
Getting my *** handed to me by the engine ATM, but giving him a bit more resistance now.
As prfen has already noted, playing an engine is not the best way to improve. If you can, find people to play. Preferably playaers that are better, and willing to go over the game with you. You will be better able to understand what a better player tells you, more than a chess engine spitting out -15.
I'm trying to beat Stockfisk lvl 6 as a way of improvement - is this a good idea?
Getting my *** handed to me by the engine ATM, but giving him a bit more resistance now.