The .htaccess file is a special hidden file that our (Apache) webservers use to configure how files will be treated in a particular directory. It is a text file that contains Apache configuration directives. A full listing of these can be found at the Apache website.
Log into the cPanel (instructions are here) and and click on the File Manager feature. When you open this tool for the first time, you will have the option to show hidden files. Check this option. You will then see the .htaccess in your file manager. If you do not see it, simply create a new file and name it ".htaccess" without quotes. Then edit the file as you wish.
Click here to learn more about how .htaccess works.