There are dual method A and method B for the PC lid. 

Method A is the default setting where the PC lid and the handle are separate-able for grinding.

And the drill-grinding is applicable.

Method B is to attach the PC lid and the handle altogether.

Take out the Black O-ring from the PC lid.

The next step is to put on the White O-ring.

*Find the White O-ring inside of the receiver*

Place the White O-ring into the groove.

Your grinder is good to go.