The public key is copied into a public key server found via google.
In kmail you can attach the public key in settings. It's in the hidden folder .gnupg
The mail recipient must have your public key before receiving "signed" messages as in the line above.
Do not sendt the key named secret to anyone.
"Hooks to PGP or GnuPG are not included in Thunderbird, but are under development at Enigmail"