Guide/Tips on Group Managing

Hey!

I´m the new Group Leader of the Plant-Based Lifestyle group.
I would love to create a dynamic group with lots of like-minded people, but I don´t understand how to use the tools and I don´t see basic instructions for groups anywhere. The page is not letting me open new threads/forums (it says something about entering valid values), and I wouldn´t like to invite people until I can be sure I can give them content and am able to keep the group going.

Any sugestions would be very appreciated.