plug in help

I'm pretty new at photoshop but can somebody help me or explain to me how to use plugins? I've download a few of them and I just don't understand how to get it to "plug in" or work. Do I have to click on them after I open up photoshop? If i do that I can't find them. Please Help!!! What do I do to use them???Any help is greatly appreciated. thanks.

You have to onstall it in your plug ins folder in photoshop for example

program files>adobe>photshop7>plugins

once its in there it should show up