Create a relation by dragging a secondary component over a primary component to display attachment points. When the required attachment is displayed, drop the secondary component to create the relation.
For example:
In this example, the top face is highlighted, and an arrow indicates a plane attachment:
In this example, a plane to plane relation is created between the secondary and primary component. The new relationship is added to the assembly tree.
If you release the mouse away from the primary component, no relationship is created, and the secondary component returns to its original orientation.