gianny on "Apply filter by IPTC metadata in image store plugin"

Hi,
i use a Image Store plugin (http://wordpress.org/plugins/image-store/) and i want to apply a filter based on metadata "credit" in the photo display in the front end.

Example: I would like to display only photos that have metadata "credit = 000"

Could someone tell me how and where i can apply this filter?

Thank you very much!

Gianni