Where do I fill the transmission on a 1977 Trans...

[Bryce B]

...Am (TH-350)? My transmission is not engaging, so I need to put more fluid in the transmission, right? If so, how much, and where can I fill it up?
The dipstick was dry. Where is the fill plug?

 

[Zimgxp]

The fluid goes in through the dipstick. Add a small amount at a time, the add mark means 1 pint low.