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- Go to System Preferences.
- Click on Security - it has a picture of a house with a padlock knob on it.
- Set a Master Password by clicking on the button to do so. If you already have one set, make sure you know what it is.Check the Encrypt contents to secure data box in the Compress or Encrypt attributes section at the bottom of the Advanced Attributes
- dialogTo turn on FileVault, click on the button labelled Turn On FileVault...
- Click OK.
- Click OK again.
- Select the desired behavior, most likely, Apply changes to this folder, subfolders and files.
- Click OK.
- After some time, the folder name (or file) should be green indicating that it is encrypted.
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