You should check out npc/merchants/shops as a reference. You can denote shops in two ways. The first is to create a static NPC at a set location like you see in that txt file (Example 1). The other option is to create a shop that can be called using the callshop function (Example 2).
Example 1
alberta_in,175,97,4 shop Weapon Dealer#alb2 82,1146:-1,1245:-1
Example 2
payon,166,106,6 script Merchant 101,{
callshop "FruitShop",1;
}
- shop MVSHOP1 -1,512:-1
Hope this helps,
~Azura Skyy