Several Coot functions require the selecting of atoms to specify a residue range (for example: Regularize, Refine (Section Regularization and Real Space Refinement) or Rigid Body Fit Zone (Section Rigid Body Refinement)). Select atoms with the Left-mouse. See also Picking (Section sec_picking).
Use the scripting function
(quanta-buttons) to make the mouse
functions more like other molecular graphics programs to which you may
be more accustomed 1.