Creating SSH Key
Ideally the following steps are completed on the device and user which you want to allow the connection from, so it will be saved in their ~/.ssh folder.
Run the following commands:
Add Keys to ssh-agent
Run the following command
ssh-add ~/.ssh/id_ed25519
Replace id_ed25519 in the command with the name of your private key file
Add Public key to Gitea
cat the contents of the public key and add it into Gitea under Settings > SSH / GPG Keys > Add key.