Multisite Error message

Today I was looking at Plug-Ins for my wordpress site, and I decided to add one that allows you to share favorite sites or something like that. I don’t remember what it was called, but as soon as I pressed “Install” or “Activate” or whatever, the screen said, “The plugin is only compatible with WordPress Multisite.”

Well, that’s fine. So I went to the next page. It said the same thing. I tried to access my dashboard–locked out. Just a white page that says “The plugin is only compatible with WordPress Multisite.”

I can’t even look at my website! (projectanyroad.com)

How can I fix this or delete the plug-in? I just want access to my site!