How to acquire/track targets MFD12 with DRS4D

I have a DRS4D radar and a MFD12 display. How can I acquire/track targets??? The manual I have tell me to put my cursor over the target then right click (this brings up the Aquire Target menu) then press the roto button. I do this and nothing happens. There is no explanation what to do with the Aquire Target menu either. Ideas???
Thanks

That is for the ARPA function of the radar.
This requires heading sensor connected to the system. Do you have a sensor connected and if so what make/model?

At this time I do not have a heading sensor installed. Would it work without a heading sensor by providing relative headings???

ARPA requires real heading (from auto pilot compass, flux gate, Sat compass or other suitable heading source) and COG (Course over ground) from GPS can not be used as a replacement.