An authenticator app asks for a six-digit code in addition to your password when you sign in. Turn it on from Security on my.quavern.com.
Turning it on
Confirm your current password. Enabling a second factor always asks for it.
Scan the QR code with an authenticator app, or add the account by hand with the setup key or the provisioning link shown beside it.
Enter the six-digit code the app shows.
Save the recovery codes. They are shown only once.
The recovery codes matter more than you think
They are the way back if you lose the device with the app on it. Each works once. If you close that screen without saving them, you have a second factor and no way around it.
Turning it off
From the same page, enter a current authenticator code or a recovery code. A password alone does not turn a second factor off.
What it does to a telephone number on the account
Adding an authenticator app demotes a verified telephone number from a sign-in key to a contact, in the same operation. A code by SMS can never replace an authenticator code or switch it off — that is the point of the ordering. Remove the app or the passkey if you want SMS to be the sign-in step again.
A reset does not go around it
If you forget your password, the reset link asks for this second step too. A mailbox on its own is never enough to take over an account.
If a code is never accepted
Almost always the clock: a time-based code depends on the device's time being right. Enable automatic time on the phone and try again.
Quavern help reference: authenticator-app/en