This is how to take a photo in a lupine field with Skogafoss in the background:

Park here: https://goo.gl/maps/fGn4Y9rEW5g3sSg26 Go across the road and follow the trail for 10-15 min. Once the trees clear, continue straight until you see Skogafoss. The lupines can be different from year to year so find a field with a good view over Skogafoss. You need a zoom lens to get the shot like the picture in description. 100-200mm is a perfect lens for this.. Good luck!