I like to use it to natural emphasise where the sun naturally hits my face. Pop a bit of highlighter on your forehead, the sun natural hits that area and gives that inner glow. If you have oily skin try not to use a creamy product here, your T-Zone is already prone to shine.
Follow up with a light sweep of the shimmery stuff highlighter underneath your brow arches to lift the face. It'll emphasise the shape and distract from any pesky stray hairs. To finish swipe down the nose and pop a little on both your cupids bow and chin to really bring out facial features.
My recommendations for highlighters to try? I love the Soap And Glory Glow all Out and Nars Albatross. But my personal favourite Kevyn Aucoin Celestial Powder - super finely milled pinky toned powder which gives the face that extra little summit summit.