Legendary Items, bro... one weapon and one class item can be equipped at the same time. The Guardian's class item is a belt, and the weapon can be any other legendary weapon, as long as it has "Guardian" in its name.
Example:Guardian's Sword of the Third Age
Guardian's Great Axe of the Second Age
Hunter's Sword of the Third Age
You can equip either the "Guardian's Sword of the Third Age" or the "Guardian's Great Axe of the Second Age", but NOT the "Hunter's Sword of the Third Age", because clearly that sword if for the Hunter class.
The class item of the Guardian is a belt. So whenever you see something like "Guardian's Belt of the Third Age", it is for you.
Where to get them?
Do the epic quests that starts outside the Walls of Moria, which means Echad Dunnan at Eregion. There you will see a dwarf outside the entrance to the Walls of Moria. Talk to him, begin the quest chain, and get your very first Legendary Items
It is also said that it is wise to change your legendary weapons every 5 levels... so the question is, how do I get some new legendary items? Simple. It is either you trade for it with other players OR buy it at the Auction House OR you kill mobs at Moria and higher level areas to get them as loot.
If you have more questions, please ask
I hope this helps...