A news post to let you know about the new method of repairing your broken tools and armor...
The below screenshots should help you figure it out, yes use a crafting workbench, place your broken item and the relevant building material it was made from, ie iron tools require iron bars, diamond tools = diamonds.
Registered rank, can only repair non enchanted items,
While Members can repair enchanted items.
The material cost is higher for enchanted items of course.
You can now forget about having to level up Mcmmo repair skill. (Mcmmo plugin is slowly being phased out at Kraftzone)