Some plugins come with an installer others come as an archive (Zip, Rar etc)
here is a pdf with the process for installing a plugin that is in an archive. (For ones with an installer you can still use this, just go straight to the run centrafuse bit)
If you download and use it, please let me know if it worked and how easy it was to follow.
Also if it doesn't work also let me know.
If you think it can be improved upon, also let me know.