After successfully signing up for VRooms, you need to add the VRooms Extension to Chrome. With the extension installed you can grab the VRooms Template file with the "New VR File" option and you can view the design in VR with the "View in VR" option. Any time you want to start a new design just click "New VR File" and a copy of the template will be added to your Figma.
Missed a step? Here's a direct link for you. Make sure you have already registered for VRooms already.