As you can probably guess from the name... Winrar is a Windows application.
For macs, you want UnRarX. Or at least, that's what I use, there might be better ones. Once you've got UnRarX set up, just put the .rar where you want it unzipped and click on it, it'll unzip automatically.
if you can't figure the rest out, you probably don't need to worry too much about using your UI since you really have no idea how to operate a computer.