setting up a acknowledgement account

There must be a huge FAQ somewhere I can never find so apologies for asking daft questions agaihn, bgut I have googled.

We've a new xymon server created?Xymon 4.3.30-1.el7.terabithia when I acknowledge an alert im not prompted for credentials to do so.

what do I need to implement to do this ?? Its on other xymon servers we run from years back etc but nobody remembers what they did (zzzz) ian