Yes, windows 7.

I use CS3, but I think loading patterns still the same way.
first go to layer from the upper bar> layer style> pattern overlay, then follow the instructions here:

the file has to be a Photoshop pattern format.

and, if you're adding a pattern of a image you got online for example.

open the image on photoshop, then go to EDIT - define pattern

and your new self-made pattern will be on the dropdown menu Juleona posted

you can turn any image into patterns (but its better if they tile, like page backgrounds etc)