Model Disorder Click on this link, then click on those atoms you would like to 'split'. Move the newly 'generated' atoms to where you would like them to be (by holding the shift key while clicking on them). Then refine.
This tool can also be used to move Hydrogen atoms to a position inidcated by the presence of residual electron density. Left click on the atom while pressing the SHIFT key - and you can move any atom where you would like it to be. Any constraints and restraints applied to that atom will still apply.