been having trouble with opening games that I've downloaded. I can't get them to open and play 

...It depends? But most of them are in a zip archive of similar, so just... double-click? What games do you mean, anyway?

The easiest is to use the itch.io app here: https://itch.io/app

You'd normally unzip the file and click on the .exe, but you'll then get a lot of warnings and blocks from anti-virus and Windows Protection. You need to manually bypass all of those. Although I'd recommend you first virus-check it before you unblock everything. Right-click the .exe and ask your anti-virus program to scan it.