The fill plug is on top of the transmission to the right and behind the shifter . It is a rubber plug that simply pulls out .
As far as the full line /level mark , there is a plug on the side of the transmission near the foot pedal area,just fill with universal hydraulic/transmission oil til it runs out . There is a screen/filter that should be cleaned once in a while also .If transission oil is very low, now would be a good time to clean it because you need to drain the transmission before removing it.