Make a flat base with your non-dominant hand. Put your dominant hand flat above it. Raise your dominant hand in a half-circling motion above the non-dominant hand, ending up around your mouth area. The half-circling motion looks like waxing a car or cleaning a table.
We mainly use above when we point to objects that are placed above each other, such as wooden blocks. We also use it when we describe a hat as being above someone's head.
Use the above sign along with the up and down signs, to help your baby better understand relative locations of objects. Also, use actual objects when signing above, to reinforce the concept visually and by touch.