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:

1. 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.

2. The alternative method for editing your hidden files is by using the edit functionality included in your FTP client, for example FileZilla.