When you open the .rar you have to download the Serum package (If you have had Serum 2 installed before, first uninstall all the files from the computer), after you installed the package you have to extract the "VR.nfo" into the same file folder you have Serum 2 installed in. After that, open the patch (If it won't let you open, go to Settings->Privacy & Security and you sdcroll down to Privacy and find the patch file, then click "Open Anyway"), then go through the patch installer and you should be good to go. I have macOS Sequoia

Hope this helped