To the non-atheist, God is not "created", He is the creator. I suspect you already knew this, right? Just picking out a random verse from the Bible, "to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever. Amen" (Jude 25).
From this, the Christian accepts that God always was, is, and forever will be. Psalms 147:5 states, "
Great is our Lord, and abundant in power; his understanding is beyond measure." So, to the Christian, God's wisdom is infinite and has always been.
God <> man... man has to learn to gain wisdom, God does not have to learn for He knows all things. This is not something you and I can tangibly see under a microscope, through a telescope, through radiometric dating, through the measurement of distance of stars using parallax or red/blue-shift... it is believed by faith. If; however, once accepts that God exists and that God created everything, then one clearly sees His intelligence is beyond measure when they look through the microscope, the telescope, physical laws, a study of astronomy, etc...
There is absolutely no answer to your question under the paradigm from which you operate (atheism), so just temporarily if you can ask yourself, "If I believed God was real and true and accepted the above verses as speaking to qualities of His character and nature, would I believe God always was, and has always possessed all intelligence?" I think you'll find that you would. If I turn the table and said if I didn't believe God was real and true, I can understand from your paradigm why the question of where God received His intelligence is posed.