You need to download 7Zip to unpack files. It's a free program, you can find it here: https://www.7-zip.org/download.html
Once you've downloaded and installed it, you'll need to right-click the SUaD archive and choose option "Extract here", then just open the newly created folder and you'll see an .exe file which starts the game. :)
P.S. here's a video tutorial about unpacking files with 7Zip: