You can't, (at least not in an easy way). Your can contact the person you bought the electronics from to get the firmware he uploaded, but it'd be best (as in you learn the most) to download Marlin [
github.com] get to know it and configure it yourself.
If you want to switch the extruder direction outside of the firmware, just turn off and disconnect power to the electronics, then flip the extruder motor connector.
--
-Nudel
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