Under Linux, the files starting with dot (.) are hidden system files. An example for such a file is .htaccess.
They can be edited in two ways:
Access the file with File Manager – open cPanel -> File manager or Legacy File Manager. After you click on the selected icon, a popup window will appear. There you should select the radio button for “home directory” and check the “show hidden files” box. After that you should be able to view/edit the chosen hidden file.