Plant it at the same depth as the rootball, or 2 to 3" inches above. Never plant them deeper than the rootball. Pland ant in sunny position make sure they have good drainage as too much water will kill the plant.

Also make sure you are planting in acidic soil. I wouldn't suggest full sun Grandad semi shade is what I've always understood

Rhododendrons will grow nicely full sun as well as partial shade. if shade is too dense it will not flower very well and branches become spindley

Grandad I disagree but can not be bothered to get into a dispute with you... life is far too short and I am far to busy. If you consider the way Rhodos are grown at somewhere like Inverewe they are not in full sun. However, perhaps your experience is different to mine!