To live in a Facebook group, you must first be an administrator of that group, if not, contact one of them and ask for permission.
Plus, the Booyah app! must be added to the group, to do this follow the steps below:
On the group's home screen, click "more" (the option is illustrated in the image below with a red square):
Note: This option will only be available when accessed from a computer.
Then go to "edit group settings" in the options window that will appear (in the image below highlighted with a red square):
On the next screen, look for the "apps" option and click "add apps":
Now just look for Booyah! in the search box and add it!
To start a live in the group, just go to the platform options, select Facebook and press the option "my wall" (highlighted below with a red square):
Now click on "choose a group" and choose the group you want your live to be broadcast on:
Ready! Now just connect to live!