dave is correct , the hot line is the front line coming out of the trans and it goes into the rear port on the exchanger .
the size of that manifold requires it be installed on the pass side of the engine . make sure you don't over tighten the compression fittings as they WILL leak , it will also crush the tube where the ferrul is and require a new line if you goof it up .
also have a large drain pan at the ready , may be best to plan doing this while doing a fluid change , this line is direct from the TC and the tc will drain as long as the line is open .
if you have an aftermarket TC , i would drain the TC , if you have a pro torque you may be SOL on a drain , the last one i saw didn't have a drain plug , i hope they remedied that ... .