...
Log into https://control.openpath.com
Go to Users and locate your user in the table
Click Filter Columns then select Namespace
Copy the the text found in that fieldThe table will refresh and show a Namespace column, it should say something like
org:parent-orgIf you have Control Center access to your customer’s org, switch to their org, otherwise ask their Super Admin for help
Create a new user in your customer’s org using your email address
Under the Email field, check Add a user from an existing namespace
Paste the Namespace from your parent org
Assign Portal Access by clicking the slider and adding the Super Admin role
Click Save
...