After you progress to the town of Gorhart, you should have some repair kits in your inventory from finding then in the world or on corpses. Simply press Start and open up to the items menu, select a repair kit, and use it on an item or weapon that needs repairing. Bam, trophy unlocked.
It is entirely possible to unlock this trophy as soon as you find a repair kit, have it in your inventory, and have a weapon or piece of armor that needs repairing. I found one in a crate in the Well Of Souls and used it on my Daggers.