The speeches of Imam 'Ali (as) in al-Kafi are a great way to understand tawhid in the school of Ahl al-Bayt (as).
Allah qua Allah (Allah as He is in Himself) is absolutely transcendent, indefinable, eternal, and unknowable. Strictly speaking, He can never be known, because He transcends all conception.
Therefore, He makes Himself known through His Names and Atttributes.
Imam al-Sadiq (as) makes it clear that the Names and Attributes are merely indications of what Allah is; they are not Allah Himself.
Some scholars say that Allah's Attributes are not separate from Him, but neither are they Him. We can use an analogy for a person. We may say that they are 'kind' but their kindness is not essentially them in themselves, which remains hidden from everyone.
The Attributes are not 'things' they are just reflected, or revealed in creation.
Imam al-Sadiq (as) said, 'Do not worship the Attributes.' The Qur'an says that you can call upon Allah using them, however. Again, just as your friend's name is not him. You can call your friend, using his name, but his name is not his essential self.
The Names and Attributes are a 'means' by which we call upon Allah.
Therefore, when making du'a, you can address Allah using any of His Names and Attributes, with the understanding that He in Himself transcends all of them and is not limited by them.
