I was given a Sato No. 3710 Telegraph Key with buzzer,
as seen on http://members.cox.net/w1vet/Practice/practice.htm
but no instruction manual.

It seems it is not meant to just act as a switch, but send voltages
down telegraph wires. Maybe the idea is you and your buddy in the
other room can practice sending messages over a wire. Perhaps someone
can recommend a web page with an explanation.

To make it just act as a switch I will just choose two points to run
wires from, to connect to my serial port to hopefully use cwirc
etc. linux practice programs, to then get my licence, and then radio.