Certain files are 'hidden' by default (such as .htaccess files). FTP clients differ in the menus used to alter settings to enable these files to be seen, but all work along the same principles.
The following is a guide to showing those 'hidden files' when using FileZilla.
Open FileZilla FTP client.
From the Menu bar choose Server
Select Force Showing Hidden Files which should be the last option.
You should now be able to see all files including 'hidden files' within the FTP remote window.
Please note: 'Hidden files' are hidden for a reason. They contain very important information about how your website operates. We strongly recommend that you back-up your web-site to a local drive before you attempt to edit any hidden files.