Step 1: Using the if
But we need to do something first, you see in the Program theres 'set /p userin1=' that will make 'userin1' what ever the user types so then with the 'if' it says (lets say userin1=hello but you will type %userin1%) 'if 'hello'=='hello' *command* so in the program it says:
if '%userin1%'=='no' goto new user. this shows that if the user types no then carry out this command with in this case is goto new user. And new user will make the user profile.
So if the player doesn't have a user account then it will make one. the next step will how you how you can do this.