I'm sorry that the pictures didn't match up to the item you received and for the late reply. I believe that we took care of this situation with you over the phone.
In situations like this, it is best to give us a call directly so we can help you over the phone. If you received a cartridge with two plugs, there is a 'general' trick to figure out which plug belongs to to the 'air vent' hole and has to be removed. If you look right below each plug, there should be only one plug that has a 1/3 inch 'internal square compartment' right underneath it. This plug would the the 'air vent' plug.
Hope that can help other customers in the future!
CisInks Customer Service Team