When you select the region to which to apply an object, such as a load or a section, you can choose between the following techniques:
Highlight selections in viewport
Click on the entities in the current viewport; for example, a face or a group of vertices. Use [Shift] + Click and [Ctrl] + Click to append entities to your selection.
Tip: You can use the Selection toolbar to limit the types of entities that you can select. For more information, see Chapter 6, “Selecting objects within the viewport.”
Sets or Surfaces
Use an existing set or surface that you have created with the Set or Surface toolsets. If you choose to use an existing set or surface, the Region Selection dialog box appears. This dialog box contains a list of the sets or surfaces that are appropriate for the object you are applying.