Binding smooth skin includes setting the smooth bind options, binding skin, then checking the binding by exercising the skeleton.
To bind skin
(Use these steps if you have already set the Smooth Bind Options you want.)
To set bind options first, then bind skin
Typically, a maximum of four or five joints influence a given smooth skin point for a character.
(When you bind skin, the Dropoff Rate applies to all the selected joints. The influence each joint has on a particular point varies with the distance between the skin point and the joint.)
You can also click Save to save the options you have set without binding skin.