New Users: Please follow these instructions for "Grid Credentials" in https://atlassoftwaredocs.web.cern.ch/analysis-software/ASWTutorial/basicSetup/grid_cert/. You will need to obtain a user grid certificate from CERN, load it to your browser and register with ATLAS IAM (identity and Access Management) as described in the documentation.
Registered Users: If you need to add roles (you should have at least the /atlas/ca rolem if affaliated with a Canadian Institution), login to IAM and request it.