Set the weight and the constraints. In the Weight box of the Weights area under Tools, you can also set the weight associated to control points. Initially, the value of the weight is 1, but you may change it at any time. If you increase the weight of a control point, the entity moves closer to the control point, if you reduce it, the entity moves away from it. If you move the control points, the shape of the entity changes accordingly.
A set of constraints to be applied to control points is available by expanding the Constraints node (see "Setting constraints on Control Points"). For example, you can control the distribution of the control point motion by properly setting the Distribution law options (see "Using the Distribution law options" for details).

How Distribution factors affect weights

Suppose you supply a certain value of the weight for a number of selected control points. Let it be W1.
Now, suppose the weight of the i-th of the selected points is Wi and its distribution factor is KDi (see "Using the Distribution law options").
The new value assigned to the weight of the i-th control point will be:

W 'i = (W1 - Wi)KDi + Wi

In other words, the actual delta applied to the weight is scaled by the distribution factor. Note that the delta (W1 - Wi) can be different for each control point.