Can I use Memoji on my MacBook Air?

Hello LittletonProgress and welcome to Apple Support Communities. It appears you are having some difficulty using Memoji on a MacBook Air.

As Memoji are tied to the same True Depth camera that powers Face ID, it is only available on devices that support Face ID. At this time, that means iPhones and the iPad Pro.

Cheers.

You will need to wait for the next macOS version: Apple introduces macOS Big Sur with a beautiful new design

Excerpt:

"Users can now create and customize their Memoji on the Mac, and express themselves with Memoji stickers to match their mood and personality."

👍

You will not need a new Mac to run the next macOS version. It ought to be released in a couple months, at most. It will be free.