We have a separate set of models for magnetic circuits, please use the “saturable core” element, this will allow you to monitor flux. There are examples/magnetic modeling. also there is a tutorial pdf in help->tutorials that covers magnetic circuits with PSIM.
If you do not want to model hysteresis there are two types of saturating inductor models in elements.
However, if you just have the standard version of PSIM you will not have access to non-linear magnetic models.