any pics? if it's a 1 piece crank it won't have cotter pins. if it's 3 piece it may need an extracting tool and a bb tool to remove the bottom bracket. if it's a screw in bottom bracket then the left side is a left hand thread.
ok i think i know the bike you're talking about now. it looks like a 1 piece crank. on the non drive side will be 2 flat, large diamter nuts. undo the outermost one (this is the locknut) then undo the inner most one. slide the nuts over the crank and off (presuming you have taken the pedal off) now pull the crank through the bottom bracket shell taking care not to lose any loose bearings.