Ok, VERY NEW TO THIS

I'm working on a school assignment, you have to have 3 characters and ask the user which one they want to dissappear, Alice, Cheshire, or Rabbit. I can get the question to pop up, but I can't figure out how to have what the user inputs determine what the program does next. I can't figure out how to have the data actually input/what type of paramaters/variables should I use?
PLEASE HELP
THANKS SO MUCH