Open your profile drop-down in the Dialpad app (top right corner). 

Select "Devices" - this will take you to the DEVICES section of your profile.

On the far right, click on the 3 dots and select "Configure Deskphone"

 or forward number below, and choose which devices to ring when you receive Dialpad calls. Additionally, in the rare event of a Dialpad service outage, calls to your Dialpad number will ring the forwarding number added to your account most recently.