320 grit is rather coarse. I would lap it up to 1000 grit minimum.
To find out which side is finer just take a dull razor and perform 10-15 laps on each side and you will "feel" it right away. This hone should be used to touch up an edge that is starting to dull a bit. It should be followed by the CrOx for best results. Please don't ask about the grit size, there is no way to determine that. Just try it and see what the results are. 5-15 laps are usually the recommended number of laps to start with. Do more if necessary and use water or shaving lather when honing to help keep it clean.

Hope this helps,