Need help with a cassette
 

Upgrading to a 9 speed Shimano rear cassette, I have the correct hub mounted already but am looking at this cassette having 4 rings already connected and 5 rings free. a few spacers and a finish nut. I am new to this part of building so I am asking for advice on the steps needed to construct the cassette and install. Any hooks I should look for, any little tweaking advice or any pointers to a website that shows how to do this..?

thanks a ton