To be able to actually use the structures as described earlier, it is necessary to define one of the atoms as having xyz-coordinates (0,0,0). This will then be the atom that will actually appear at the spot of the atom that is replaced by the structure. If you use the Save As Structure command this will be done for you.
Select the File → New command Click No (do not save changes) Build methane Replace three of the hydrogens by chloride atoms and pre-optimize Delete the remaining hydrogen Select the central carbon atom Use the Structures tool → Save As Structure ... command Enter a name like trichloromethyl Note that the selected atom (currently the C atom) will be used as anchor
The new structure will appear in the structures menu and can be directly used.