Hi Lisa, great question! We see ourselves as separate from enlightenment, separate from the primordial awareness/timelessness that is Dzogchen. Dzogchen practices seek to show us that this is our natural condition, that at the root of our mind, we are this awareness/light. At that level, there is no separation between us and the objects of our perception - the 'outer' or external world as we normally experience as separate from us. There is no dual reality. Or you could say, there is both dual reality and nondual - this distinction stops making sense. It is just something useful for talking about the world and ourselves, a trick of perception and language.
Desire is seen as an expression of our perceived separateness. When we desire something outside ourselves - whether it's chocolate or another person - we seek to bring it to us. We are experiencing it as separate from us and we seek to join with it in some way. This is really the nature of our existence - desire. And we are created out of desire, in terms of sexual union. All of creation is born from desire - this pull of separateness towards union.
So in Vajarayana traditions of all types, including Dzogchen, we are asked to work with desire, instead of trying to repress/control it through discipline, like other traditions (including other branches of Buddhism) ask us to do. It is a different approach. Every desire is seen as a reflection of our desire for ultimate union - to be one with ourselves, with Dzogchen, with the heart of the universe. So the practices are meant to help us see the true nature of desire, and to work with the energy in this way. In other words, we can work with our desires, which exist within our illusion of separateness, to overcome this illusion.
And that is a lot of words to explain something that is really meant to be transmitted beyond words, teacher to student. This is another important component of Vajrayana traditions - that true learning and understanding happens beyond words.