Public key usage on Thunderbird (with Enigmail OpenPGP Key Manager)

The Enigmail OpenPGP Key Manager is designed to be simple to use with a clean, powerful interface.

You can access it from within Thunderbird/SeaMonkey via the OpenPGP menu: OpenPGP > Key Management.
You can also run it as a stand alone application by appending -pgpkeyman to the command that runs Thunderbird/SeaMonkey, e.g. on Windows: "C:\Program Files\Mozilla Thunderbird\thunderbird.exe" -pgpkeyman.

For more details refer here.