All in One SEO plugin not working!

I’ve installed the All in One SEO plugin however it doesn’t seem to be working at all like what I’ve seen in tutorials on the web…there doesn’t seem to be anywhere to add a general description for the site, and the only thing that comes up is a bar on the right side when editing pages, which I also don’t understand as when I type in keywords, they actually show up as text on my page. I don’t know how to use this bar and what the ‘above line’ and ‘under line’ mean.
The plugin is not showing up under my ‘settings’ either.
Please help!! I can’t find anything other than those tutorials which seem to be out of date ??
Thanks!