This will give you instructions on how to fully download the mod
rar file is opened, you will likely see a ReadMe file that can be opened in Notepad. rar file, you will need another application to open it, such as 7-Zip File Manager, which can be downloaded on the Microsoft Store rar file to your browser while others will redirect you to a Github page with the mod's latest version to download
If it does, we'll update this guide, but you're stuck with vanilla GTA 5 until then. Unfortunately, Script Hook V hasn't been updated to support the Epic Games version. If you're playing the game through Steam, this can be found in \SteamApps\common\Grand Theft Auto V\.