It's a little late now to be asking for advice. Presumably you've been gradually increasing your distance and thus building up your strength, ensuring your bicycle fits you properly, and experimenting with nutrition to find out what works for you???

If so, you should be set ... just ride like you've been riding.

If not ... well ... good luck out there!

My article with tips for riding a century: http://www.machka.net/articles/century.htm