Show Cue System

I'm a newbie, so my apologies if my problem has already been raised. I'm using the professional version 11.7.0 64 bit.
I have an audio file cue which I need to use a number of times. When I attempt to add a "call cue" cue; the call cue window in the cue properties window does not list any of my audio cues. I suspect I'm not doing something correctly. Any help would be much appeciated.
Peter

You must set "activation mode" as "Callable" for the audio cue you want to call repeatedly.

Regards,
Lluís

Blindingly obvious now you've told me.
Many thanks.
Peter