Connect your microphone to the PA system as usual by plugging the mic line into the mic input on the PA and adjusting the sensitivity and equalizer as needed.
Plug the guitar cable into your guitar effects if you have any. Plug the last effect on the chain into the amp head, but do not plug the amp head into the speaker.
Use the heavy duty speaker cable to connect the amp head to the Talkbox. The cable should go from the output to speaker plug on the amp head to the input plug on the Talkbox.
Connect the output of the Talkbox to the input on the speaker cabinet using another heavy duty speaker cable.
Tape or tie the end of the plastic tube coming out of the Talkbox to the microphone or microphone stand. It should be nearby your mouth and the mic so that it is easy to pick up to put into your mouth when you are ready to make use of it.