There is a tool that allows you to set password protection for a specific folder. Just go to the Advanced > Password Protection section of the Web Hosting Control Panel.

Click on the New Password Protected Area button.

Select your domain from the “Drop-down menu” or type the full path to the protected folder in the “Path” field (e.g. /www/my-best-domain.com/protected_folder). Enter the username and the corresponding login password. Click the Add PPA button to confirm.

If you need to set more users, repeat the above steps, just use different usernames.

IMPORTANT: If there is an .htaceess file within the protected folder, the protection would not work, so either remove it or consider another password protection technique.