There is a cap right next to the gear shifters. It's about 1-3/4" dia or so with a hex head on top. The hydraulics share the same fluid as the transmission.
Filter is inside the tank.
The power steering can not be adjusted on a Massey Ferguson 165 tractor. Check to make sure the hydraulic reservoir is full. This is usually the cause of most steering issues.
What year is a massey ferguson 165 with a serial number of 37786240?
a 165 Massey-ferguson oil pan holds 8 1/2 quarts
1974 http://www.tractordata.com/farm-tractors/000/7/4/746-massey-ferguson-165.html
1973
were do u find a serial number on a 165
1974
1971
in the oil filler hole
1973
that would be 1968