Two of a Kind is a PoE Achievement. It requires that equip two unique items with the same name.
In Path of Exile, you can equip two rings. Therefore, in order to completing this achievement, you need to find two unique rings with the same same.
You can search unique rings from Path of Exile Trade.
Type Filters:
I choose two Praxis Paua Ring and it costs me two Chaos Orbs.