IMPORTANT: If You plan to install Joomla or any other script with https, You should first install free SSL certificate for that domain (how to do it check HERE).

1. Log in to Your DirectAdmin (how to do it check HERE).
2. If You have more then 1 domain, click any of them to get to main menu of DirectAdmin.
3. Click "Softaculous Auto Installer".
4. Mouse over Joomla icon and click "Install".
5. Fill in all necessary fields.
6. Delete "joomla30" in field "In Directory" if Joomla should not be in any directory.
7. Click "install" on the bottom of the page, after some time Your new Joomla installation should be ready.