"Prepared" pizza base - does that mean cooked?
I would imagine, if the book is of reasonable quality, by prepared, they mean one that you have prepared earlier. If there's a recipe for pizza base in the book, that's probably what they'd like you to use.

Personally, if you're going to the trouble of making home-made pizza, make your own base. Invariably, the pre-made bases you can buy from stores taste like chalk.

There's a few topics here that may be useful:

What is the best flour to use for pizza dough?

How to make pizza crust thin and elastic at the same time?

For Pizza cooking at home. What is the best alternative to the pizza stone?