Adding custom field to display in archive grid of SG Window

Hi,
I’d like to add a custom field to display with image and title on the archive grid view but am struggling to see where to change the code. The jet pack portfolio template looks like it might do this, if I added rhis detail as the excerpt, so I had considered just diverting to that php script, but when I do nothing seems to happen!
I have set up a custom post type to load affiliate product data feeds into and so would like the price to appear in the grid view of the archive, in case someone has a simpler solution