No plugins? No new users? No HTML/CSS editor?

I’ve got three issues I have no idea where to start on troubleshooting.

1. There is no menu to allow plugin installation in the admin site. I’m an admin, and I don’t have the functionality at all.
2. I can’t add new users to the site who are not “an existing user on this network.” So, how on earth do I add new users, then?
3. I don’t have the ability to edit the HTML or CSS of the template I bought from Solostream. My footers aren’t showing up, despite having widgets set to be in them, and I have no idea what’s going on because I can’t see the template code.

Any help would be greatly appreciated.