Hi there,
By default, Ruby support 02 footer position, footer1 and footer2
You need to create footer3 position via templateDetails.xml file, please take a look this tutorial
Next step, go to template options -> Layout tab -> footer section -> Add new columns -> select 4,4,4 column option. See https://imgur.com/Ci7awX6
After that, assign the new footer3 position for new column then you can create new Joomla module -> assign it to footer3 position.
