This is something you really need to wait until your child is ready for. For my eldest it was 2.5yrs and just before she started pre-school.
For six months before, we talked about using the toilet and also she watched "Once Upon a Potty" which I bought as a set from Bookazine. It had a video with a corny song, a book and a doll with a potty. I bought the girl version.
Then I also talked about the "Nappy Fairy" who would come to collect all her nappies when she didn't need them anymore. When she could use the toilet all the time during the day, we would put her nappies in a basket at the end of her bed, and during the night the Nappy Fairy would come and take them for a new baby. In return she would leave a gift!
The combination of school to look forward too, the Potty song (she can still sing) and the Nappy Fairy worked for us.