...Under the hood...find the transmission lines (in/out) to the radiator...
Then look around for these lines to connect to another 'unit'...possibly finned...
The additional cooler will of course provide greater temperature reduction in the transmission temperature. I realize this is not very specific in the location, color or size but it's a simple way to
locate a 2nd or additional/optional cooler.
Generally it could mount to an open/available space...attached to the finder well, near the radiator or even the firewall....

The new optional coolers by speed shops or mgfs. may use a bright color...purple, bright green...etc.
Hope this is helpful