To remove pedals: point the crankarm towards the front of the bike. Put the wrench on the pedal so the wrench handle is pointing towards the back of the bike. It won't line up exactly, so move the crank arm up or down to get the wrench handle more or less horizontal. Push down on the pedal with one hand, and push down on the wrench handle with your other hand or foot. Or, if you can, just squeeze the wrench handle towards the crank. If the pedal is really tight, you may not have enough leverage for this to work.