Do I have to do everything for you?
The tutorial I gave you should give you all the basics that you need to add any item to any shop.
[sigh]
Just find Harin in LIST_NPC.STB
look across her entry row till you find the "sell id" column(s)
now open LIST_SELL.STB and go to the row indicated by Harin's "sell id"
Add teh id for the potion into an empty space
Save the STB and put it back into the client and server.
Note:
You don't need to do anything with LIST_SELL_S.STL unless you actually added a new sell tab (i.e. a completely new row in LIST_SELL.STB)