First you need a personal secret key. Create one via the option menus in "Keys" or import existing secret keys. Afterwards, you can download your friends' keys or exchange them via QR Codes or NFC.
It is recommended that you install OI File Manager for enhanced file selection and Barcode Scanner to scan generated QR Codes. Clicking on the links will open Google Play Store or F-Droid for installation.
Several applications support OpenKeychain to encrypt/sign your private communication:
Conversations: Jabber/XMPP client
K-9 Mail: OpenKeychain support available in current alpha build!
Please report the bug using the issue tracker of OpenKeychain.
If you want to help us developing OpenKeychain by contributing code follow our small guide on Github.
Help translating OpenKeychain! Everybody can participate at OpenKeychain on Transifex.