First off, make sure you don't use clipless pedals at least for now until you can heal that up. Being clipped in will be much harder on your knees because you cannot move your foot around on the pedals if needed to get comfortable. Next as mentioned above, don't use high gears and pedal real hard just gear down and spin it up a little more. Pace yourself, take it easy and don't apply too much pressure as you pedal. Just the weight of your legs and momentum should be all you need to keep going except when climbing and try that out of the saddle if you can.