1. Login to your Plesk Panel.
2. Expand the advanced options section.

Click on ‘Password-Protected-Directories’.

2. Click on ‘Add Protected Directory’.
3. Enter the name of the directory.
4. Enter the title of the protected area.
5. Click OK.
6. Click on directory name.
7. Click on ‘Add New User’.

Enter Username, Password and click OK.

There you go. You’ve successfully password protected your website.