FileVault Encryption on Mac
From the Apple menu in the upper left-hand corner, choose System Preferences, and click on the Security & Privacy icon. Proceed to click on the FileVault tab to access the FileVault settings. You must first unlock the settings by clicking the lock icon on the bottom left corner and submitting your account password. Settings to enable FileVault can be found via the link below.
FileVault encryption can be used to help prevent unauthorized access to your documents and other data stored on your computer. When FileVault is enabled you can't log in automatically. A password is always required when you start up your Mac so that OS X can unlock your startup disk.