Create new items?

I would like to know how I could create new items for the game.

I was able to create the item on the server-side but for the client side , I always get an error telling me that something is wrong with the item I just made.

Anyone know how to do it properly?

How about you tell us what is wrong with the item?

Give us screenshots, errormessages, maybe what you've done serverside and what you've done clientside then we may be able to help you.