All account providers give you a backup option for logging in. It may be using a different phone or printing off backup codes. You will be asked which backup option you want to use when you first enable 2FA. It is strongly recommended that you take the time to set one up. If you lose your phone or authentication key, it breaks, is stolen or you forget it you can use the backup option to get into your account. Remember you only need the second factor to login to your account on new devices so this really isn't an issue most of the time.
Each account provider has their own procedure for enabling 2FA. Check their security settings to find out. However if you want to turn on 2FA on your Mount Royal email account, check out