Two files are required to create a template in Joomla. First is the index.php file, in this file we can place php code where the content of site should go and second file is templatedetails.xml which includes all the configuration settings and parameters required. One CSS file is also required where we can put our CSS related work. All these files will work together and produce content for Joomla website.
Now create a new folder inside templates folder. Inside a folder create one text file name as index.php file and other is templateDetails.XML file and one css folder. Inside css folder create template.css file. So we need to link template.css file to index.php file. Place the content which is given below in templateDetails.XML file. In this file we will add template related information and basic module positions settings.
Next is to create a zip file and install the template from Joomla administrator panel. Once installed it will appear under template manager where you will mark it as a default to display on front end website.