Normally, you'll have a content directory something like:
C:\users\public\public documents\My Daz 3D Library\
This directory has all the subdirectories like Data, People, Runtime\Textures, etc.
So what you do is open the Rar or Zip in a work directory you make, then navigate through the files and-or directories in the opened rar/zip file until you locate any or all of these:
Data, Runtime, People, etc. (they'll all be together, once you 'drill-down' through everything).
Highlight those files and right-click on them, you'll get a drop-down context menu from which you can select 'Copy'.
Having done that, right-click on your 'My Daz 3D Library' and from the Drop-Down Context menu select 'Paste'.
You may get some dialogs from Windows, just click 'OK' on any that come up.
You won't see anything in your 'Smart Content' since there's no manifests in most of these 3rd party files, but you can find them by opening your 'Content Library' tab in Daz and scrolling through the stuff in there. Many are categorized by author, so pay attention to who created the content.
Now, if the rar-zip file you open has another zip-file inside, like this: IM00090699-01_SomeName.zip, right-click and copy the file, then -instead- drop it here:
C:\Users\Public\Public Documents\DAZ 3D\InstallManager\Downloads (it's right above your 'My DAZ 3D Library' directory).
That file *will* appear in 'Smart Content' after you run DIM (Daz Install Manager). In DIM, Just click the box 'Work Offline', then start the install cue.
Do this a few times with different files and you'll get the hang of it.
