Need help with adding in a new private server

hello all i need some help with adding stuff to a private server and want to know how i can do it like adding new items or price's to NPC
- adding D13 sos items to NPC
- adding D13 som - sun to NPC
- adding D13 som to Mobs with a nice rate

im new to this so would like good info i have searched on google youtube about changing and so but i cant do it adding thos php codes and all , i also downloaded RefShopGen also dont know how to use it so i would be realy happy if some one could realy help me step by step and show me how i can do this
if you want to talk with me in private MSG me and i will send u my Skype or FB

Thanks already for all who would help me .