How to assign an Admin role group to a user in Exchange admin center?

Step 1: Sign into Office 365 admin portal via https://portal.office.com

Step 2: Click on Admin from the left pane and navigate to Exchange admin center.

Step 3; Navigate to Roles > Admin roles.

Step 4: Click on the role which needs to be assigned to a user from the list of admin role groups.

Step 5: Switch to Assigned tab and click on Add button.

Step 6: Select a user from the suggestions and click on Add.