Go to your skills menu (the one with the icon that looks like a hand) and drag the Weaponcrafting Icon to your toolbar.
Click the Icon, this will open up a list of all the different categories of weapons that you can craft. Select one and the sub-types will be listed, select the one you wish to make a drag its icon to the toolbar as well.
Each weapon has a specific recipe that you can view by right clicking on its icon. Make sure that you have the items necessary.
Now find a forge and target it, left click the icon of the weapon you want to make and the timer bar will start. When the timer bar is finished you will have one of 3 outcomes:
1. You succesfully make the item
2. You fail to make the item but lose no materials
3. You fail to make the item and lose some of the material
Hope that helps, and happy crafting.