Leave edit mode (tab key).  Select one of the spheres.  In the edit buttons, go to Modifiers panel and click the Add Modifier button.  Click on the Armature option.  In the box under the new armature modifier that starts with Ob: type in "Armature", which is the name of your armature object that we looked at before.  Click on the "Envelopes" button to deselect it.  For something like this you don't need it.  Actually, I avoid it most of the time, it never does quite what I want.

Do the same thing for each of the other spheres.