Just get a pump that fits the top of a quart of ATF (available at most NAPA & other reputable parts stores), & pump fluid into the fill hole (after going through all the steps in the check level instructions) while the engine is idling in neutral. When it's full, let the excess run out & replace the plug...it's now at the proper level...
I'm in the dark about riff's advice too, so don't feel alone...![]()