How to make a member of a team its owner?

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 All admin center > Teams.

Step 3: Click on Teams on the left pane and then click Manage teams.

Step 4: Click on a team from the list.

Step 5: Select the Role option and click on Owner respective to the member