Thank you for serving.
Can you tell us a little more about what kind of bikes these are? Are they spin bikes (with a flywheel) or regular stationary bikes?
Regular stationary bikes often have different levels (1-10 or 20). You could experiment with what the different resistances feel like at each level and then design a plan where you warm up at an easy resistance for 5-10 minutes and then vary your workout with intervals of higher resistance for anywhere from 30 seconds to up to 3-5 minutes. Make sure you cool down, too for at least 5 minutes. Spin bikes work on the same principle, but usually have a dial to turn that raises or lowers the resistance. You want to raise resistance to simulate hill climbing, but not so much you are hurting your knees.
Make sure the seat is set appropriately for your height (not too low), so you can extend your leg with just a slight bend in your knee. I am assuming that even on a FOB there is someone responsible for keeping the equipment in shape in the gym. Maybe they can show you how to set up the bike, at least.