[MicroMonkey]

You have to execute that command as admin, hence the SUDO. I hope this helps :)

sudo chown -R www-data:www-data /var/www/html

This changes the ownership of the whole html folder to the apache group. You would have to switch ownership again if you wanted to overwrite files through FTP since you would no longer be the owner, but you can google how to add a user if it matters to you. I like it because it keep me from accidentally overwriting any files when I get drunk lol

You can do this to change back
sudo chown -R $USER:www-data /var/www/html