Where do you connect a tachometer to check the Revolutions Per Minute at an idle on 1993 GMC Sonoma

I have replaced the throttle body and need to verify engine speed

Asked by for the 1993 GMC Sonoma
Engune idle speed is not adjustablle! That screw is only a throttle stop, ecm has control over idle through IAC valve!!
1 more answer , 4 more comments
Negative side of the coil.
There are 5 wires running to two separate plugs, which one is negative, and do I pierce the wire?
The white wire with the pnk/blk, the other white wire is a digital signal for the instrument cluster, if the tach is digital use that one.
Thanks a bunch
I was tied up earlier, No Worries.