When you meet the conditions listed for the repair level, then you can use dark matter to repair the equipment. When you check a piece of equipment, you will see its repair level information under the gear's condition and spiritbond percentages. If you want to repair your equipment by yourself, you can upgrade your crafters. You just click on the mender's menu which will allow you to repair other items in the inventory or armory chest. It is a good thing to regularly repair your equipment, as long as the condition is below 100%, you can repair them, which is to prevent them from falling even lower. You can find these NPCs in towns or at aetheryte camps. You can pay Gil to mender NPCs and let them repair your equipment. Before you repair your items, all equipment with 0% condition will go, so how should you repair them? In FFXIV, having a good set of equipment can give you a favorable advantage in battle, but as you continue to running battles, crafting, and collecting, your equipment will be worn to a certain extent, if you often check your equipment, you will find that their conditions are getting worse and worse, when their conditions are 0%, you need to do something for them.