To enable the static aircrafts go to your X-Plane graphics menu and tick the draw static aircrafts checkbox. Aircrafts will then be placed in your scenery automatically. The airlines depend on the parking position assignment in the scenery. If no proper airline could be found a blank livery will be used.
Please note: If a jetway is not connected to a static aircraft instantly after loading the aircraft is out of the jetway limits. Especially smaller aircraft doors types are often too low to get a proper connection. This is not a bug, at least not in combination with the WorldJetways extension.