In LTspice a SPICE directive is text placed onto the schematic that passes directly into the netlist. It may be entered either as a single line or as a block of several lines of text. Since ENTER closes the text edit box, a new line must be started by typing either ctrl-ENTER or ctrl-M.
The text edit box may be accessed either via the drop down menu item: Edit -> SPICE Directive or by pressing its Hot Key, if one is assigned ("S" is the default). Also, the s