Unzip the zip file to a temp folder. There is normally a "Runtime" folder inside the zip file. If you installed any Daz content, it will be in "My Library" somewhere. Inside My Library, there should be a Runtime folder for Poser content. Merge the zip file runtime with your runtime. Make sure Daz Studio recognizes My Library as both Poser and Daz content. If the zip file contains a folder called "content" that is the same as My Library. Merge the contents of "content" directly to My Library.
Edit: The Daz New users help forum is full of info on this and other topics:
http://forum.daz3d.com/viewforum.php?f=97
Edited by mediasponge on 02/17/12 03:19 PM.