Ok lets get to the point, these are the process on how to install an NPC script.
1. Get a full working script, you don't want your server to crash.
2. Copy and paste the script to your athena/NPC/custom.
3. Don't forget the file name of that script, for example you named your script goldroom.txt
4. Go to your athena/NPC and open scripts_custom.conf
5. Type npc: npc/custom/goldroom.txt at the end of the line.
6. Putting a // before the npc/custom/goldroom.txt will disable the script.
7. Save and restart your server or if you are too lazy to restart the server, use your GM account and type @reloadscript