I am unable to get Time Machine to recognize the My Passport external drive. When I installed the My Passport and it asked if I wanted to back up with Time Machine, I checked “decide later”. Cannot figure out how to get back to a place at which I can now answer that question “yes.” I’ll be grateful for any suggestions. Thank you.
Through your applications, look for the time machine backup app and follow the steps to setup a new backup. It should allow you to select the location for the backup.
See if the following link helps