Step 1:
Click on your account name to expand the menu on the bottom right corner of your screen → select Team Members

Step 2:
Add your team member's email address → You can choose to invite as an admin/editor → select invite.

Be sure to select the Project/s you would like to allow your team member/s to gain access to.

Step 3:

You can manage your team member's access here ↓

➠ You can also add team members and guests individually to each project: