Create a Subgroup object by double clicking on "Subgroup" in the Objects Toolbox. From the Subgroup dialog you manage which points and polygons are contained within the Subgroup.
To add points and / or polygons to the Subgroup, select them in the normal fashion, then hit the Add button in the Subgroup dialog. Points and Polygons will be updated to indicate the current number of points and polygons contained within this Subgroup.
To remove any points and / or polygons from the Subgroup, select them in the normal fashion, then hit the Remove button in the Subgroup dialog. Points and Polygons will be updated to indicate the current number of points and polygons contained within the Subgroup.
To remove all points and polygons from the Subgroup, use the Remove All button. You will be prompted to be sure that you want to do this, and then all points and polygons will be removed from the Subgroup.
Hit the Select button any time you want all of the points and polygons contained within the Subgroup to be selected. This can be a handy option if you ever become confused as to which points and polygons within the document are members of this Subgroup.
Once youve defined the members of this Subgroup, you can use the Hierarchy Panel to make it a child of another object within the object hierarchy.