Step 1. Download
Requires macOS 10.11 'El Capitan' or newer.
Step 2. Install it
Drag the app into your Applications folder. Once it's installed, double-click the Poll Everywhere icon to run it.
Mac PowerPoint user?
Don't worry Poll Everywhere for Keynote also works with PowerPoint.
Keynote 6.2 User?
Poll Everywhere is not compatible with Keynote 6.2. To use Poll Everywhere, please upgrade to Keynote 6.5