Generate one. Which OS are you on? Look up for a tutorial, you'll certainly find a good one. Edit: you either have to install GPGTools (for OS X, https://gpgto

Generate one. Which OS are you on? Look up for a tutorial, you'll certainly find a good one. Edit: you either have to install GPGTools (for OS X, https://gpgtools.org/ https://gpgtools.org/), GPG4Win (https://gpg4win.org https://gpg4win.org) Windows, or gpg for linux. To use GPG in Thunderbird you'll also need Enigmail.