Well Molecular Geometry is basically the geometrical arrangement of the atoms in a small or large molecule. In order to do this you will have to think back to some general chemistry. For this you need to know your hybridization states, primarily sp2 and sp3.
Also the molecule above is Glycine (Gln, G) an amino acid used in protein translation. this will also help you to determine how to order the backbone of the structure which is basically N-C-C (Nitrogen-Carbon-Carbon).