The use is very simple and intuitive, you can send and receive emails the same way you would with any any other email service.
The encryption, decryption, signature and signature authentication is automatically generated by the application.

Further information on sending/receiving messages and file attachments can be found here.

For your business, you can use your own domain name and have a professional encrypted email service. This is what it would look like yourname@yourcompanyname.com (or net/org/etc.).