This is the book I used to help get my son used to the idea of using the toilet and wearing jocks! There is also a girls version. 

“Learn how to toilet-train your child in six easy steps while supporting and motivating him through this important developmental stage.

This kit features an easy-to-follow parent guide by expert child psychologist Dr. Janet Hall PhD to help implement toilet training in six easy steps; an engaging board book designed to support children with toilet training, two illustrated reward charts with space for stickers and 48 reward stickers to motivate children and positively reinforce successes!”