Your download starts automatically. If it didn't start, download Rotato manually.
Open the Rotato Installer.dmg file from the downloads list at the bottom left corner of this window.
Drag and drop Rotato to the Applications folder.
Open the Launchpad or Spotlight, type Rotato and launch the app.
Now that Rotato's up and running, check out the Quick Start Guide and Rotato for Figma.