Public SSH Key in GitHub
Publishing your public SSH key to GitHub can be used when you're installing a new Ubuntu Server
A public SSH key is what you give to a server you would like to access.
If you need to generate your own SSH public and private keys, you can use this tutorial.
After you create your account on GitHub.com, click on your icon on the top right and click on "Settings"

On the left click on "SSH and GPG Keys", then click on "New SSH key."

In the new window you can name the key and provide the public key. Leave the option selected for "Authentication." Afterwards click "Add SSH key."

If you generated your key using the guide you can open terminal and enter cat ~/.ssh/id_ed25519.pub
to get your key.
After you click save, you will need to login again.