There are two major things you do when sharpening a saw chain. Sharpening it and filing down the "depth gauge" if needed.
For Stihl chains, they have the following "Depth Gauge Tools" available...
[Used for checking top plate angles, cutter length and for filing correct depth gauge setting. Available sizes: .018", .020", .025", .026", .030", ..031", .035".]
How do I know which depth gauge tool to get for a specific chain?
I'm using the Rapid Super L Full Skip Klassic (RSLFK)
Here are their various chains...