I have included a diagram that shows the location of the fill plug for this model odyssey. If you were looking at the engine bay, look past the intake tube and then down and thats about where it is. If your Odyssey has had the 2nd gear recall done, then a tube would be going into this plug hole and that would have to be removed to fill it. Please let me know if you have any further questions, thanks.
It is #7 in the diagram