Weapons and ArmorWeapons and armor can be brought and sold from the Armory in Novigrad, and from other players in the Flea Market. They can also be made with the right combination of Ore and with enough Smithing studies at the Name Fabrication in the Industrial Park of Novigrad.
To equip your weapon or armor, go to your house and you should have the option to equip best there (underneath Inventory section). In order to be able to equip weapons and armor, you need to have the right level to equip them. You will find this information under Campus Prime and then the Wildcat Memorial Library. The more powerful the weapon or armor, the more higher level you will need. A piece of equipment will have a maximum strength value - this is the most that item will add to your stats when equipped. For example, the maximum strength a Dark Matter weapon will add to your attack is 100.
Weapons and armor can be damaged in combat, but you can have them repaired. In order to repair weapons, you need to visit the armory in Novigrad. It will cost credits to repair your weapons.