MacOS comes with a tool that can facilitate the encryption of files on your MacOS device. This tool is known as File Vault. File Vault uses XTS-AES-128 encryption with a 256-bit key to limit access to authorized users only, on your start-up disk. Encryption occurs in the background when your mac is awake and plugged into power. Decryption requires the recovery key created when turning File Vault on or your account password.

Follow below steps to enable File Vault Encryption on you MacOS:

1. Select System Preferences on the apple menu followed by Security and Privacy
2. Click on the File Vault tab
3. Click on the padlock icon on the bottom left to unlock the preference pane then proceed to enter the administrator name and password
4. Click Turn on File Vault

For other users with accounts on your Mac, click the enable user button then you will be prompted to enter their passwords which should be done so that they can be able to unlock the disk. User accounts added after turning on File Vault will be automatically enabled.

A recovery key should be configured considering that you might need to decrypt the drive or mount it to another Mac.

An iCloud account can also be configured to decrypt the drive for devices using OS X Yosemite or later soft wares.