Then, you can use proper functions of Multiwfn to study these real space functions. There is no unique way to study them, for example, you can plot them as a curve/plane/isosurface map, perform topology or basin analysis on them. If you focus on topology properties, I think you should first check examples in Section 4.2 of manual, where I provided many examples of using the topology analysis module of Multiwfn.

The Multiwfn manual is extremely detailed, you can find very rich information (introduction of theoretical backgrounds, usage of different functions, practical examples and hints) from it.