Well you can't change JUST the name you gotta delete everything if your using Windows then follow this:
- go to file disk C: then
- go into user and then
- click the file with ur name
- then type in the top (where it reads "this pc > local disk C: > users > Name") and type in \appdata then
- go into file roaming
- find renPy
- and then find name of the game
- and delete everything in the file