How do I wire overdrive or lockup in my full manual 98+ 4R70W?

Using a length of original vehicle harness, connect pin #4 to switched 12V source.

Connect pins #7 & #8 to the accessory prong of a toggle or rocker type switch inside the vehicle. (See diagram in tech install manual)

Connect the other prong of the switch to a good source of chassis ground.

Using a separate switch, connect pin #3 to accessory prong, connect other prong of same switch to a good source of chassis ground.