How do you turn on the paging / all call jack on the ACTU1A main board? I don't have an output there.

You need to go into Station/Paging Devices
Select relay 5 and then select what page group you want it to be a member of eg all call page group or page group 1 etc. (it can be associated to more than 1 group)

Then when you dial #30 for all call page or #3101 for page group 1 it will also come out of the RCA output from the ACTU processor.