Hello PMDG-Experts

I use to fly the PMDG 737 for a long time but there is one item that happens to fail everytime - may be I forget to do one important thing :%
If I have a route and want to fly a HOLDING at one waypoint, I have read that I have to open the HOLD page, get the name of the waypoint int the scratchpad and the press LSK6L.
Fine that works. On the leg page there is also a leg called "hold at xyz".
But the sucking plane never obeys! It ignores the Holding and coninues the route.
What am I doing wrong?
Do I have to DELETE the original waypoint (where I choosed to hold)? Is there any restriction (speed, Inbound course) that I have to watch?