Elsa going to a new home.

Elsa is our beloved 8 year old American Shorthair. She has lived with us all her life and has been free to come and go as she pleases. She has free reign of her current neighbor hood, so much so that we have never had an indoor litter box. We will be moving to a new home where she will need to be an indoor cat. Any and all advice regarding this transition would be greatly appreciated. Thank you.