HADashboard img

Hi All,

I’m a newbie to the world of HA.
So far (using HASS.IO) I’ve integrated all my z wave gear and I’m happy with how I’m travelling.
I’ve created a custom skin on HADashboard which is working, but I cannot figure out where I am meant to store an image to use as a background on my skin???
By this I mean - I’ve created an ‘img’ file in my custom css folder. But how do I physically save an image to that folder?
Thanks in advance!