If you want to make someone an owner or view who's an owner of an existing team:
To the right of the team name, select More options > Manage team.
Select the dropdown next to Members and guests to see all team members. The Role column on the right tells you if someone is a team member or team owner. To make someone an owner, select the dropdown and then choose Owner.
If you want to make someone an owner or view who's an owner of an existing team:
Tap Teams and to the right of the team name tap More options > Manage members.
Tap the name of the team member and then tap Make owner.