To create a group, click on "clients"
Click on Groups
Click on new group
Fill in all the details of the group
Click on Save when you filled everything
You can now add rooms and clients
You can either find a client or create a new one
Click on add once you filled in all the informations
Add rooms to the clients you created
Fix a price and choose a way of payment
And click on Add
You can of course add other rooms to other clients by repeating this manipulation
Refresh your page to see your group reservation
Here they are! That's it! You're done!