With Ask for a code when I sign in switched on, a password alone cannot open your studio. After your password, Studio Operations texts six digits to your verified mobile number.
Turn it on or off
Settings → Account → Signing in → Ask for a code when I sign in → Save changes
Sign in with the code
Enter your email and password, then type the six digits from the text message and choose Open my studio. The code screen expires after five minutes. Choose Send a new code if the text does not arrive. You can also enter one unused recovery code instead.
Remember this computer
Remember this computer for 30 days is ticked on the code screen. Leave it ticked on your own computer and you will not be asked for a code there again for 30 days, even after signing out. Untick it on a shared or public computer. Changing your password makes every remembered computer ask for a code again.
To change the email used for signing in, use Change your sign-in email.