First, make sure your team member(s) are added to your Hired account (see 'Adding Coworkers to your account').
In order to add a team member to a Position, select the relevant Position on your left-hand menu. Next, click on the + icon in the upper-right corner and click on the blank space next to your name.
You will see a dropdown of your coworkers that have a Hired profile. Select each coworker you would like to add. Now you and your hiring team can shortlist candidates, share team notes on candidate profiles and review candidates from this Position in your ‘Interviews’ tab.