Components, when added to an instance in your level, are placed by default at the location of that instance. However, they can be Transformed, Rotated, and Scaled as necessary in either the Details panel or the Viewport similar to the method in which you can Transform Actors.
You can select Components for transformation either by clicking on their name in the Components window or by clicking directly on the Component in the Viewport. When Transforming, Rotating, and Scaling your Components in the Viewport, hold Shift to enable snapping. This snapping requires that snapping be enabled in the Level Editor and uses the Snap Grid settings from the Level Editor (see Viewport Toolbar for more information on Grid Snapping).
Exact values can also be entered for Location, Rotation, and Scale in the Details panel for your selected component.
Transforming, Rotating, or Scaling a parent component will propagate the transformation down to all child components as well.