It is always safest to download directly from the creator's official Patreon page to ensure you have the latest, cleanest version.
Because .rar is a compressed format, you will need a utility to open it: Scene Everyone's Girl (Patreon).rar
If it's a "Scene" pack (often for CharaStudio or VAM), you typically move the .png cards or scene files into the specific "Saves" or "Scenes" directory of that software. It is always safest to download directly from