I'm not sure if anyone answered this already, but there's two ways:
When you have third party content, most of the time you have to do this, copy and paste into the correct folders, but if the file has a DIM configuration there's a faster way.
When I say DIM conf. I mean a zip file with the name that starts with IMO and a bunch of numbers. All DAZ.com content comes like this and some third party also.
Just paste this file in C:\Users\Public\Documents\DAZ 3D\InstallManager\Downloads and open your install manager that comes with DAZ, select work offline and after loading the products should appear to be installed. The additional advantage is that the products should appear in your smart content tab, if you like to use it.
Hope it helps.