Feel the prana in breath - the intangible part of it, the invisible part of it, the immaterial part of it. It comes if you are attentive between the two eyebrows; then it comes easily. If you are attentive in the gap, then too it comes, but a little less easily. If you are aware of the center at your navel where breath comes and touches and goes out, it also comes, but with less ease. The easiest way to know the invisible part of breath is to be centered at the third eye. But wherever you are centered, it comes, you begin to feel the prana flowing in.