Make sure you're logged in.
gh auth login
Then, you can install the extension via:
gh extension install github/gh-copilot
At anytime, you can update the extension via:
gh extension upgrade gh-copilot
Usage is simple:
gh copilot [command]
Where it has 2 different options for the [command] parameter:
explain Explain a command
suggest Suggest a command
Using suggest:
gh copilot suggest -t shell "copy a local file to a server via ssh"