Once fermentation has begun you need to punchdown the grape skins from the top of the must into the liquid.  This will allow the color and flavor of the skins to mix with the wine during fermentation.  This is done 2-3 times per day.  When fermentation starts there are few skins on the top and then as it is in full swing 4″ of skins float on the top.  Finally, when fermentation is complete the skins barely float on the surface.