If you have a new phone number:
Sign out of the app and sign in again with your new phone number. You will now have a new user connected to your new phone number.
Inform those who have shared keys with you (the board in your apartment building, friends, work, etc) that they have to send keys to your new phone number and delete the keys connected to your old phone number.
Connect any locks you own (eg. the lock on your apartment door) by going to settings, press "add private locks", choose your lock type and sign in with your details.