There are some basics here:
https://www.renderotica....ntent-in-Daz-Studio.aspxOne thing not mentioned there: Different vendors may use different zip file structures. When you open the zip file, you'll want to look for folders with names like "data", "runtime", "People", "Props", etc. These are the folders that go directly under your "My Library" folder. However, some vendors also zip those up within the "My Library" folder itself, so you'll need to either unzip those one level higher, or (as I always do) drill down within the zip file until you find those folders and unzip to your base library folder as usual.
Another piece of advice (learned from years of struggling with Poser runtimes and, now, DAZ Studio installations): Think about an organizational scheme early, and get in the habit of organizing everything as you get it. DAZ Studio makes this *much* easier than Poser (at least up through Poser 9 or so... haven't used it since then), because you can add "Categories" that are completely separate from the physical install locations. As an example: I've actually set myself up with separate libraries for each store (DAZ Install Manager, here, R'osity, freebies), because I like to track where things came from in case I ever need to double-check terms & conditions (some freebies say "not for commercial renders," for example). But then I have everything categorized into my own system that makes sense to me, so that when I'm in the middle of trying to be creative, I don't have to try to remember where it's installed (even within a store: I've noticed that, for example, rooms and environments just from DAZ may show up under /Library/Architecture, /Library/Environments, /Library/Props/Environments, etc...).
Likewise, Future You will thank you for quickly getting in the habit of setting up metadata (compatibilities, types, tags, etc) for everything you acquire that doesn't already have it, but that's a somewhat more advanced topic.