In order to do that you need to get your Keybase public and private key installed locally. Here's how:
1: Save your public Keybase key to a file called something like
keybase-public.key. You can get this by clicking on the key Fingerprint on the keybase website:
2: Save your private Keybase key to a file called
keybase-private.key. You can get this by clicking on the 'edit' link to the right of the key Fingerprint on the keybase website:
3: Import the keys to gpg:
gpg --allow-secret-key-import --import keybase-private.key
gpg --import keybase-public.key
You may wish to securely delete the private key file now to ensure it doesn't fall into the wrong hands.
4: (Optional) Make the Keybase key your default key.
Get the keyID with
gpg --list-secret-keys and make a note of the Keybase keyID.
~/.gnupg/gpg.conf and add a line:
That's it - you can now use normal GPG commands to encrypt and sign things using your Keybase key.