iPGMail is an App for iOS which is able to work with PGP. You can import keys from pgp.mit.edu, from keybase.io or via iTunes File Transfer (this is also how you transfer your private key if you like).
To decrypt an email you have to copy the PGP block to your clipboard and paste it into iPGMail - not very comfortable but it works.
To send an encrypted mail there is a "Compose" view. Enter your email there and you can send it directly from the App. You can either configure it to use your iOS Mail Settings or provide your own STMP connection data in the App settings.
You can also use it to just encrypt and decrypt files.