OK, I think I've got it. Looks like the instructions call for removing the steel line that goes from port #18 (power beyond) to 3 pt hitch. Then I basically hook the 3rd function valve in series between these points, the hose from the loader valve will go into the P port of the 3rd function valve and the T port of the 3rd function valve will go back into the 3pt hitch.
View attachment 434935
Does that sound right?
I guess this means that I need to make sure I'm not using the 3rd function and 3pt hitch adjustment at same time.