Example:
From Merchant.txt in c:\...\mud3\envir\
04Potion_Bichon 0 189 255 (PotionShop)_Jarad 0 1
04Potion_Bichon = the file name(no spaces in name
0= map number 189=X coordinates 255=Y coordinates
This will equate to a file in c:\...mud3\envir\market_Def\
called 04Potion_Bichon-0
Notice the file name has -0 after it, you must include the - followed by map number.
(PotionShop)_Jarad is how the NPC will be named on screen. If you like you can just call it Bob...in which case it would be:
04Potion_Bichon 0 189 255 Bob 0 1
The final 2 numers are the facing direction of the NPC, usually 0 and the NPC image number from the NPC.wil/wix in Data directory.
HTH