One of the key benefits to the team admin account is the ability to create listings for your team. That includes:
assigning a listing to multiple agents on the team that could host an Open House so no repetitive setup is necessary
allowing agents to simultaneously host an Open House and keep track of which visitors signed in with which agent
Here's a video that walks through how to do it when creating a listing for the first time.
To add/remove agents on a listing that's already been created, open the listing (select the listing from the My Listings screen) and select the "Paired Agents" shown on the map (top right of the screen) to edit the assigned agents.