You can create a mapping using the Create Mapping tool from the Mappings pane.
or
[if the target object is a sub-object] Select one or more objects in the Source pane and then select an object in the Target pane .
A visual link is drawn between the objects and a small symbol is displayed on the source and the target object icons. The mapping details display in the Mappings pane.
If the target object is an object owing sub-objects, a selection dialog box is displayed to let you select one or more sources for the target. Then they are displayed in the Object Sources sub-tab of the Mappings pane. Besides, sub-objects that match are automatically mapped and are displayed in the Sub-Objects Mapping sub-tab.
If the target object is a sub-object, you also need to select one or more object icons in the Source pane. The mapping expression is displayed in the Mapped to sub-tab that you can modify. You can also add other source objects using the Add Sources tool in the Sources sub-tab.