wait, it's still not working. You have to go to your own group's page. Just the group. Visit the tab at the top that says ADMIN AREA. You click there, and it takes you to, well, the admin area. Then you click the first tab there, that says MANAGE MEMBERS. Once you click there, on the options that will appear on the right, you can change the Join Requests behaviour.
Right where it says JOIN REQUESTS: you change the option from ARE NOT ALLOWED to ARE AUTOMATICAY APPROVED. And that's it! sorry if it's hard to follow, I cant add refference images to guide you.