I've got a 220 but haven't installed extra POIs on it yet. If it works in the same way as the other Zumos then you need to download Garmin's POI Loader program onto your PC. Run POI Loader, follow the prompts and it will load the POIs onto your Zumo.
Bear in mind that POI Loader loads one POI set, and if you subsequently load another set of POIs, these will overwrite the first set. So if you want to incrementally add POIs to the Zumo, you need to add the new POIs to a set on your PC that already contains existing POIs. In other words, if you load your Norwegian dealers as POIs, and then decide to load up a set of POIs for speed cameras in Norway, then both sets of POIs will need to be loaded in one hit.