As others have mentioned, it is difficult to tell you what to do if we don't know what product you are trying to install, but here are some general guidelines:

(1) Nothing bought at Rendo is going to show up as smart content unless you create the entry in the content database for it yourself.  Frankly I find the smartcontent to be pretty much useless in finding anything anyway.  It will show up under your content libraries if it is installed correctly.

(2) Generally, unless it is specifically for Genesis or Genesis 2, it is going to show up under your poser library rather than your DAZ one, which means it should be installed under /My Library/runtime and not just /My Library/  This is intuitively obvious to anybody who started with DAZ 3 or earlier, and a lot murkier if you started with 4.5

(3) In addition (Thanks DAZ! cough) if you have been using DAZ since before the new content installer you have stuff in two different places - Everything installed pre-installer is going to be in your document root under documents/DAZ 3D/Studio/My Library, while everything POST installer will be in /public documents/My DAZ 3D Library.  DAZ does allow you to put content in as many libraries as you want, as your content library grows you will understand why that is a good thing.

Anyway, what I do, is unzip all the contents to a scratch directory.  There will either be a My Library folder or a runtime folder (sometimes both), or the folders /data and /people.  In the case of the My Library folder, go into it and copy everything into which of the two locations you have your library in.  In the case of everything else, just copy the existing folders into your library.