How do I find keynotes on my macbookair

In the Applications folder. If it's not there, you can download Keynote for free from the Mac App Store:

https://apps.apple.com/us/app/keynote/id409183694?ls=1&mt=12&v0=www-us-mac-keynote-app%3Dkeynote

Use Search (magnifying glass icon at right end of menu bar) and search for Keynote.

Or look in Launchpad or open Finder and use the Finder "Go" menu to go to the Applications folder.

If it isn't on your MacBook Air, go to Apple menu > App Store and search for Keynote.