This tutorial shows several calculations of NiO in the crystal-field approximation. Within the crystal-field approximation the solid is approximated by a single atom in an effective electric potential. This is a huge simplification and for many properties not valid. One should not confuse the crystal field potentials with real potentials. They are introduced to mimic the bonding in a crystal. Non-the-less it is a rather useful approximation for many local properties of a solid. Local moments, orbital occupation and several core level spectra can be well described to some extend on this level of theory. The most important part though is that the local symmetry can be reproduced, thereby the theory captures degeneracies and local multiplets.