It's all about fuel my friend, this I have learned as a fellow newbie. Grab some Heed or similar supplement from your local bike shop to add to your water bottles, a couple or three bananas, a handful of gel shots (for the second half when it's harder to stomach real food), and maybe some fig newtons, pb&j sandwiches, energy bars, or whatever. Eat every half hour or so after the first hour. Bring too much food, it's light. Load up on sunblock, esp tops of your legs. Empty a water bottle every hour minimum. Stretch on the bike frequently.
Good luck!