You maybe know about any good online resources for nap training?
* lay down
* set a 20 minutes timer
* close your eyes and try to relax, don't open them until the timer rings, even if you are not sleeping
* repeat daily, ideally around the same time every day
If you have troubles getting up afterwards, try a powernap: drinking one cup of coffee right before napping. The caffeine will kick in at about the same time your nap ends.