Two general statements:
1. You cause your body to adapt by doing something you're not used to.
2. The adaptation is to make you better at repeating what you did.
Generally, rides are either done at a pace faster than you're used to (for a given duration) or they go further than you're used to (at a given speed). The first will cause your body to be better at going fast. The second will increase your endurance.
If your goal is to be able to ride 60 miles, then I'd suggest doing one longer ride a week, gradually increasing the distance of the ride until you get there. If you want to do it more quickly, I'd also suggest once a week doing a shorter (relatively) but faster ride like an interval workout. A spin class may also work for this if you enjoy them.
For a 60 mile ride, you're probably fine with oreos. It's not a crazy long distance to ride and you don't need to be perfectly optimal in your nutrition. As long as you take in some carbs in the first half, you should be fine.