How to add a second device to your Duo Authentication

Log into https://mynetid.rice.edu
Click Add a new device.
Complete the two-factor authentication.
Proceed with the device enrollment process. For example, to add a landline as a second phone number. Select Landline and click Continue.
Enter and confirm the second phone number, and click Continue.
Select the device you would like to be the default. You may want to enable "automatically send this device a Duo Push" in the When I log in option if this is a mobile device you will be using most often with Duo, then click Save.