To use the Multi-user editing feature
- Enable the Multi-User Editing Plugin in your Project
- Restart Editor
- Go to Project Settings > Plugins > Multi-User Editing
- Enable Multi-User Toolbar Button
- Set Display Name
- Pick an Avatar Color
- Go to Project Settings > Plugins > UDP Messaging
- Expand the Transport section
- Add a Static Endpoint with IP Address: Internal IP
- Connect to ITC or RWTH-VPN and click on the new Browse button in your toolbar
- Create a session and distribute the project to your partners. Everyone needs to have the same state before starting the sync
More information can be found here