To password protect a folder/directory, follow these steps in cPanel:
1. Login to your control panel using your account username/password at http://www.yourdomain.tld/cpanel
2. Click on "Password Protect Directories" under Security
3. Browse to the folder which you want to password protect
4. Click on the name of the folder
5. It will present you a form. It has two parts and you have to submit both separately:
a) Security Settings
Password protect this directory (check the box to the right). Then name the protected directory (enter a generic name of the protection such as "My Protected Folder"...this is only for the security window that visitors will encounter. This name will not change the name of your folder.)
Submit and it will protect it. Now step (b) for adding username/password. Go back or browse to the same directory.
b) Add/modify authorized user
Enter the username/password and save it.