You will select a primary device on your Devices page. Each time you log on, you will be prompted to authenticate using your primary device. The login page provides the option to change devices and select a different device to use for authentication.
Authentication normally will only work from your primary device, although some web applications may give you the ability to authenticate with a secondary device for your current session.
If you need to set a different authenticator as your primary method, please follow the instructions located on this page.
Now, access the My Devices page. It displays the devices you currently have paired with your account. Your primary device will be highlighted in green.
Finally, click the Primary slider to select the device that you want to make your new primary device.