Predefined Metal Complex Geometries

Select the 'ML6 Octahedral' from the metal complex structures and place it in the
     drawing area 

Notice that six dummy ("Xx") atoms have been placed around the metal center in an octahedral fashion.

Select all the dummy atoms by right-clicking (or click and hold down) on one and use
     the 'Select all Xx' option from the pop-up menu. 

The Ligands structure submenu contains a number of ligands which can be used to replace the dummy atoms. The Structure menu can, however, also be reached via the atom pop-up menu.

Right-click on one of the selected dummy atoms and select the 'Ligand/CN' structure
     from the 'add structure(s)' menu in the pop-up.

Notice that all dummy atoms in the selection are replaced be the CN structures.