XF 1.5 Overwhelmed by permissions/usergroups, need help

Overwhelmed by permissions/usergroups, need help. I want to make it so only staff can post in some areas and members can't, but it thinks i'm (the root administrator) part of "registered" (which I want to change to 'members', so it's the default members group? But apparently that's not what I'm thinking it is?). So when I disable "registered" in my Announcements & information area, I can't even post there as an admin.

When I go to try and create new groups, permissions, etc - I'm incredibly overwhelmed by all the options and such.

I just want a members group where they can't post in certain areas and a staff group where they can, and then my group - the admin group - with all privileges.