It is easy but it will take practise and a slightly different mindset. Firstly I will post a fragment of Robert Waggoners Gatewaye to Inner Self.
"If you control the dream, who made the grass green and the sky blue? Who created the new scene when you cam around the corner or flew through a wall into a new room? Did you control all that new scenery and detail into being?"
He observes here that although we may manipulate the dream scene we are not in full control, no matter how strong our lucidity. Now this doesn't pose much of a problem but you must be weary that the dream does not always go your way and may unexpectadly change things.
When lucid dreamers first start their journey they don't focus on the intent of wanting to make a fireball appear out of their hand but instead perform the action and expect the fireball to follow. While this may seem very obvious it seems to be a major stumbling block.
All it really takes to become omnipotent is your focused attention and intent.
When I first started lucid dreaming I had a few goals, one of which was to fill a valley with water using telekinesis and another was to sink a mountain into the ground. At first I kept trying to use telekinesis and all different magic etc but I soon realized that all these have no meaning in dreams. While the visual may be amazing it is not what is causing the water to levitate. I realized that when I focused hard enough the mountain would collapse on itself without any struggle on my part.
Your potential focus and attention increase with each lucid as the quality and lucidity increase. It will become easy and then you can truly do whatever you want.