The OBD port is on the lower left of the driver's footbay. Stick your head in there, feel with your hand the lower left edge of the panel and the OBD port will be pretty obvious. There are access slits cut into the leather (and it may even be labeled, i don't recall).
I get them every once in a while but they always clear on their own. Typically a misfire. .. Could be due to a very wide range of reasons but in my case is it is always the case of leaving my car undriven for a long period of time. Probably gas line had a bubble or battery was a bit under charged (more likely the case actually).
(I've never had the light come on other than for a misfire.)