In Drive, select the file you'd like to encrypt. Click the "More actions" icon in the toolbar and select "Encrypt" from the dropdown menu. You'll know your file is encrypted because a lock will appear on your file. To open an encrypted file, double-click on the file, enter your Guard security password and click "OK".

The first time you use email encryption you'll be prompted to set it up. Click "Start Setup" and enter a password, confirm the password and then enter a secondary email address in case you need to reset your password in the future. Then click "Next". Click on the "Help" icon on the right side, you can take a "Guided Tour for Guard" or learn more about Guard by clicking "Learn more".

Click "New email" and click the "Options" icon at the bottom of the new email window. Select "Sign email" from the menu. Now your email will be sent digitally signed. This provides verification of the senders authenticity, thereby helping to prevent message tampering.  

A Guard encrypted email will have a "Lock" icon next to the subject line in your email list. When you open the email you'll be prompted to enter your Guard security password. You can also tick the box next to "Remember my password" and select how long you'd like to stay logged in from the duration dropdown menu. Once you click "OK", you'll be able to read the email.

To decrypt a file, click on the encrypted file, click on the more actions icon in the toolbar and select "Remove encryption" from the dropdown menu. Enter your Guard password and click "OK".

In Mail, click "New email" and then enter all of the details for your email. Click the lock icon at the bottom of the window. The lock will close and it will ask you to enter your Guard security password. Then click "OK". Now just click "Send" and your email will be sent encrypted.