Log in to the Decoin exchange and access your “Account” on the top right side of the page by clicking the image icon. When you login into your account for the first time, you will be prompted to enable Google 2FA using either your phone or Google Authentication.
In your account page, locate the “Security Level” bar. Underneath it, you will have an option to enable either “SMS Authentication” or “Google Authentication”.
Choose the authentication you desire and follow the instruction.