In the Search Form you will find different alternatives to select the work centers. For example, you can select work centers directly, via manufacturing orders, via their start or finish periods etc.
Further down in the window you will see group settings that allow you to select how to calculate the loading plan. The following alternatives are available:
You can also select many of the settings in the Search Form later on in the list by right-clicking and using the Info Menu.
The loading plan is then loaded by using the Display List under the window functions.