How can I create a public event in a FB group?

When I try to create the event, I can’t find an option to make an event public. This is a festival-type event and we want the public to find this info on our group page. The group is public. On the first page in creating an event, it asks for the name of the event and the dates. Then it shows a box for choosing privacy; it gives the group name, but the whole thing is grayed out. There’s no way to choose any option, much less a public option. What do I do? I haven’t found any tutorials that cover this.