How to install aquaclear filter?

I recently purchased a used aquarium that came with an aquaclear 50 filter. I got the aquarium from friends, so with new carbon and whatnot, I'm not afraid to put it in my tank. I have the filter put together, but I can't figure out how it actually goes in the tank. There's nothing to hang it along the side, and I don't have suction cups or anything to stick it to the side. Am I missing parts or something? How does this filter go into my aquarium?