If you're going direct from ASMO to Poly, I recomend driving to save time, but if you decide to take WDW transportation, it's not too bad. Simply take the MK bus, then take the Resorts monorail around to Polynesian. Easy.
Once at Polynesian, finding 'Ohana is easy; it's on the upper level of the Great Ceremonial House (the main building). If you take the monorail, you walk into the building from the monorail station and cross to the opposite side of the lobby; 'Ohana is on the left. If you drive, you will come into the GCH from the parking lot directly under the monorail tracks. Walk to the opposite side of the lobby and take the stairs up to the second level.
As I said, I recommend driving, which will save you time both incoming and outgoing; once you're finished eating at 'Ohana, you'll be STUFFED and won't want to spend a lot of time standing around at the monorail and bus stations to get back to ASMO.
