You need to be a project owner yourself to add/remove other owners.
Project owners can administrate the project, e.g. change the project name or invite other members.
Follow these steps to add/remove the project owners:
- Open the project
- Click the more icon in the bottom tab bar
- Click the option Members
- View owners: All project owners are marked with a filled red star
- Add owner: Click the empty star next to the person who should become an owner
- Remove owner: Click the filled star next to the person who should no longer be an owner