This question is wide open. If your goal is only to make the distance, then all you need to ensure is that you can be comfortable throughout the duration. For novices, the biggest comfort issue is usually the rear. You need to ensure that you can tolerate riding in the saddle for 4 or more hours.
Avoid the temptation to push big gears at a slow cadence. During your saddle time, concentrate on smooth pedal strokes as opposed to doing reps of leg presses.