The Dev Hub is our production org. Scratch orgs are registered against a Dev Hub and can be managed from there. Execute the following command in a terminal (you'll be prompted to enter your username and password in a browser window):
sfdx force:auth:web:login --setdefaultdevhubusername -a Unum_DevHub
It's possible to have multiple Dev Hub orgs. If you want to change to a different Dev Hub, you must specify your defaultdevhubusername
setting with this command: