Don’t need an external application, we can easily add password to protect Folder by creating an Encrypted Disk image from folder in Mac OS X El Capitan, Yosemite or any OS X versions.
Hiding folder is a simple way to protect your Data somehow. Take a look at How to hide Folder and view hidden files in Mac OS X El Capitan.
Apple provides Mac OS X with a feature that can encrypt a folder to a new disk image. The encrypted Folders will be protected totally by your own secured password.
Steps to add password protection to a Folder in Mac OS X
Commit the instruction below:
How to open the Encrypted Folder and Contents with password protection in OS X?
You got the new disk image of the Folder after the encryption process is completed. Just open the disk image and fill your own password. We would recommend not to check “Remember password in my keychain” option.