The optional debris guard is installed with the 4 and lock nuts that are in your tool set.  The debris guard simply bolts to the removable plastic base that is clamped on the tube next to the gearcase of the line/brush cutter attachment

The line cutter (blade that cuts your line to the right length when you bump the line spool to get more line) is screwed on with the blade facing out. The blade and screw are in your tool kit.