When SPH parts are selected in the parts menu, clicking the "Pack (Fill)" button displays the following panel in the lower region of the parts menu.
This panel allows you to fill SPH objects with SPH nodes.
Pack the selected objects with SPH nodes. You will be prompted for the fill material, the SPH node size and velocity to use for the packing operation.
Delete all SPH nodes in your model.
Delete the SPH nodes in the selected SPH objects.
Delete the SPH nodes in a box defined by the XYZ coordinates of the origin and the size of the box in the X, Y, and Z directions.
Delete a single SPH node, by specifying its local IJK index. You can use the Examine option to interactively select SPH nodes, and determine their index.