Simple answer: You can't.
Longer answer: The Cannith Crafting system cannot create items, it can only add magical properties to items that already exist. The only exception is arrows and bolts. If you've already done the crafting tutorial quest, the steps it walks you through really are pretty much the whole system. If you haven't, go to the crafting hall in either House Kundarak or House Cannith and talk with the NPC at the entrance. He'll guide you through step by step with plenty of dialog options for asking extra questions.
Now, since crafting isn't a solution to your problem of never having enough non-mundane shuriken, here's what is a solution to that: You need a Returning shuriken - comes as a single instead of a stack of ammo, functions as unlimited ammo, and can have magic properties just like any non-ammunition weapon. These drop as random loot sometimes, but it's rare. There are usually several available on the auction house, but if you're a new player you may not have enough to pay the requested price. If you get one of these, you can accept the properties it already has or modify it with crafting, but if you're new you probably won't have the crafting experience required for higher level abilities for a while.
The most reliable low level source of Returning shuriken is the quest chain in the Seal of Shan-To-Kor adventure pack. The end reward list for the quest chain has a high chance (guaranteed on the third completion of the chain) of containing the named shuriken
Shadow Star. At a somewhat higher level, the chain reward for Cult of the Six will often include
Snowstar. Both of these are named items, which cannot be altered with crafting.