Absolute beginner, looking for advice on getting started

I'm trying to start things up and really not sure what to do next and would really appreciate any advice!

​

My main goal is offline information and media storage. I don't have too much to start out with at the moment so working with mostly a blank slate. Work is getting rid of old equipment, so I've got the basics. I have 2 desktops now (aside from my main personal laptop), both older Dells, Optiplex 390 & 7010 pretty much blank slate. I also picked up 4x 1TB HDDs, and 5x 500GB SSDs. They were all free so I just grabbed as much as I could. I've upgraded the drives in my 390, on the 7010 done nothing other than download Windows 10 for now. I'm not exactly computer illiterate, but this is a layer of complexity deeper than I am accustomed to and I am definitely out of my element.

​

Ok so what do now?

What OS should I use?

What Software should I get for actually storing, managing, and accessing this stuff?

What should I do with the SSDs?

​

Think my starting idea on all this is stuff like saving Wikipedia, iFixit, handbooks, cookbooks, maps, guides, etc. Then starting to save media, songs, books, movies/tv, whatever. First thoughts are to use one desktop for work stuff and less permanent storage, then the 390 for larger storage and more of a classic 'home computer' type like when I was younger. Not in any hurry to get all this accomplished right away, but looking for the next steps I should be taking and what direction I should be going. Any and all advice is welcome!