Drive the car get the transmission oil hot.The automatic transmission fluid is changed by removing a drain plug at the bottom of the transmission. The drain plug has a square 3/8 tool to remove it. Allow the oil to drain ,replace the drain plug seal, and refill the fluid trough the dip stick hole (yellow dip stick is located just under the battery area of the engine compartment. Refill with Honda ATF Z1 fluid and check with the engine switched OFF. Drive the car, and switch off the engine recheck the oil level and add oil if required. The trans fluid maintainence light needs to be reset with a scan tool.
There is lots of debate amongst automotive technicians regarding transmission flush vs transmission drain and refill. On transmissions where you can drain and drop the transmission oil pan to remove and replace the internal transmission filter and inspect for debris on the bottom of the oil pan once it is removed you get the majority of the transmission oil out any way (some older cars used to allow you access to drain the torque converter which was great). The conflict arises (as with engine flushes) is where you have an engine or transmission with sludge in the valve body. On higher mileage transmissions there have been many cases of a transmission (that would probably fail soon any way) having failed after the transmission had been flushed. Transmission flushing machine manufacturers would claim other wise but I have seen and heard the same story from automotive instructors and technicians. If the transmission is healthy flushing will do no harm what so ever but a lot of people don't think of changing the transmission oil until they are experiencing a transmission problem of some sort. Arguments for and against both sides.
With regard to Answer #2. All good step-by-step advice, but the author doesn't mention the substantial amount of used oil left in the torque converter...which is undrainable unless removed by special equipment that some service places have. So, I feel it would be like changing your oil and not replacing the filter--leaving a quart of dirty oil in the system. So I go ahead and pay the $75 or so to have that done professionally.