Hello and welcome to the Mazdas247 forum.
Your question requires some additional information.
Are you trying to top it off? this should not be needed, it is a sealed unit.
Are you draining it and re-filling it?
Are you talking about the automatic transaxle housing or the differential?
To put transmission fluid into the transmission, there is a dipstick with a black rubber handle to the left of the 12 volt battery (as you are standing in front of the car looking at the engine bay). Take the dipstick out and that is how you put fluid into the transmission.
Are you draining the old fluid?
Also check out the numerous other threads in the engine/drivetrain section of this forum.
Good luck!
