Here are the instructions on how to play Skribbl.io using the game object in Gather. As the host , only you should only click "X" to near the Skribbl.io game object to start. You will need to create a private room so you can invite your friends!
Creating a room
Click "Create New Room"
You will need to click "Create Private Room". Don't click "Play!" because that will take you to a random room.
Copy the ENTIRE link
Message the ENTIRE Skribbl.io link in Gather Chat "Nearby"
Joining the Room
Players can now press "X" to interact with the Skribbl.io Game Object. Paste the entire Skribbl.io link in the "Join Room" text box.
Players will need to type in their name and click "Play!"
If you did it correctly, you should see you and all of your invitees under the word "Players"