For Mac and Windows. You’ll also need Roblox Studio and a RoStack subscription.
First open: drag RoStack to Applications and open it. If macOS says it can’t verify the app, open System Settings → Privacy & Security and click Open Anyway. You only do this once; RoStack updates itself after that.
First open: if Windows says it protected your PC, click More info, then Run anyway. You only do this once; RoStack updates itself after that.