How do you make a teammate a co leader or staff ?

As this question is a month old, I will reply anyway, go to the team member list (this for the recent version after the update to the Team feature) by tapping on the button for your team, in the list you select the player you want to see profile of and there at the bottom of the top banner is a Promote (green colored) button on the left side, press and select to proceed to making them Staff, then repeat that to make them Co-Leader.