Before you start, make sure that you have turned editing on.
First you need to create the groups. To do this go to the Participants section of MyCourses from the sidebar.
From there, click the gear on the right and select groups
There you will be able to manage groups. Select Create Group, fill in the appropriate information and then save it. Note that if you are naming the groups by the date they will take place it is a good idea to create them in a chronological order, because the groups can be sorted by either date created or the name.
Once you have created all the groups you need to add them. Create a new group choice activity (or open an existing one), click Edit and select Edit settings.
Go to the Groups section, select the groups you want to add and click the Add button to add them.
Once you have added the groups click each individual group to set a limit for each round and press enter once you have set the limit to save it!
When you have added all the groups and set the limits for them, save and you are done! Please consider the value of the setting "Allow choice to be updated" depending on your needs.
In the case of the example the complete page looks like the following.