With the webserver up and running I needed to be able to FTP into the var/www/html directories to upload my HTML and CSS.
As Ubuntu server comes with SSH installed be default I decided to use that for FTP instead of installing something like vsftd (Very Secure FTP Daemon). FTP over SSH turned out to be a much simpler and quicker setup.
Warning: These steps do not restrict access to folders outside of the /var/www/html directories. As such this setup is not recommended for any kind of production server.
First create a new directory under /var/www/html:
sudo mk dir newdirectory
Create a new user and give the user a password:
sudo adduser ftpuser
sudo passwd ftpuser
Finally give the new user the permissions that they need. Change the directory ownership and group: