This is EXPERIMENTAL software. Use at your own risk!
First you need some keys. Import or create them via the option menus in "My Secret Keys".
It is recommended that you install OI File Manager to be able to use the browse button for file selection in OpenPGP Keychain.
If you want to contribute, fork it and do a pull request on Github: https://github.com/dschuermann/openpgp-keychain
Please report it in the issue tracker of OpenPGP Keychain.