ModelRisk uses Monte Carlo simulation to calculate the risk and uncertainty you face. This page will give you the background information on Monte Carlo simulation.
Together, these short videos cover the most important features of ModelRisk needed to build your own models.
These videos describe the ModelRisk features that make it extremely quick and easy to switch from @RISK to ModelRisk
These videos run through example models which you can download and follow along with. You can find many more example models here.
ModelRisk has a wide range of tools that simplify addressing common but technically-challenging risk analysis problems. Here are videos explaining a few of them