itch.io

If you're on win11 I think you can extract by right-clicking and selecting "extract all" from the drop down list because IIRC Win11's archiver includes RAR files. If you don't have that option when you right-click the archive file you can enable it by downloading & installing 7Zip or similar archive program.

Remember to scan anything you download from the Internet for viruses before opening it of course (in Win11 the simplest version of this is right click-> more options-> "Scan with Windows Defender"), but once you've done that it should be fine and anyway you're unlikely to get a virus on Itch.

If Windows prevents you from opening the program once you've extracted it, click on the "more" button on the little blue pop-up window and it will give you the option to run it anyway; if you've already scanned it for viruses it should be safe enough.

Click on one of the empty cells on your side of the trade screen.

I know, it confused me too.