To do the baby sign for over or above, your dominant hand starts with palm looking down in a flat position above your non-dominant hand, which should be waist-high in the same position. Your dominant hand should then go up to the area below the nose.
We mainly use over to introduce our babies to location. We use it in the context of play and to teach our baby the location of items as he learns to explore the world around him.
Use over in conjunction with objects and location references, for example, over the head or over the table.