Useand on the toolbar to make and remove links between objects.
The general process of creating links is to build the hierarchy from child to parent. You click Select And Link on the toolbar, select one or more objects as children, and then drag the link cursor from the selection to a single parent object. The selected objects become children of the parent object.
Once objects are linked, any transformations applied to the parent are also applied to its children. For example, if you scale the parent to 150%, the size of its children and the distance between the children and the parent are also scaled by 150%.
A complex mesh hierarchy can be displayed with the links visible, or even with the links replacing the mesh objects. To display links, first select the linked objects. On the Display panel , turn on Display Links to see the links. You can also turn on Link Replaces Object to see only the links and not the objects.