Et si tu lisais son topic? 
Je cite :
1. Extract the Archiv.
2. Put the npcs.jar into your plugin-folder
3. Put the folder "npcs" into your plugin-folder (all Npc-data will be saved there, also
LANGUAGE-FILES have to be there!)
npcs-folder (default is: "/plugins/npcs" if you want to change the Folder-Dir
you have to edit the npcs.properties-File.
4. Put the npcs.properties into your root-dir, like server.properties
5. If you want to migrate your old NPCS, you have to set "npc_migrate=" to true
in npcs.properties. To get more Information about Migration, continue reading.
6. Give the Groups the command /npcs, if you want to let him to use this commands (change in groups.txt)
If you create NPCs, npcs_simple/npcs_trader/npcs_itrader will be generated.