help with my rev counter

Hello all

I have just received my vdo tacho for my 300tdi.

In the instructions it tells me to put a rpm meter on a pull to see the rpm and then set the switches on the back of the gauge.

How has fitted one and do you have the switch settings as i do not have a rpm tool.

Here is my gauge.

This from another site any help?
https://forums.lr4x4.com/topic/1986-vdo-rpm-counter/
This is the link within the first one: https://reedx.net/rev-counter/

cheers mate.