If you read Acts 9 you will see that St. Paul’s revelation came directly from God.
15 And the Lord said to him: Go thy way; for this man is to me a vessel of election, to carry my name before the Gentiles, and kings, and the children of Israel.
16 For I will shew him how great things he must suffer for my name’s sake.
Also, St. Paul started preaching before he met with the Apostles.
20 And immediately he preached Jesus in the synagogues, that he is the Son of God.
As mentioned above I believe St. Paul received this revelation before he met with the Apostles. After he preached Jesus we see he was taken to the Apostles.
27 But Barnabas took him, and brought him to the apostles, and told them how he had seen the Lord, and that he had spoken to him; and how in Damascus he had dealt confidently in the name of Jesus.
Also, if we go to Galatians 1 we get some more evidence that St. Paul received his revelation directly from Christ.
*12 For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ.
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He reaffirms that his teachings are directly from God, so that he might begin immediately.
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15 But when it pleased God, who separated me from my mother’s womb, and called me by his grace,
16 To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood:*
However, important to note is that he does add:
18 Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days.
Here he reaffirms his audience that even though he is teaching from the revelation he says came directly from God he did spent 15 days with St. Peter going over what he has been teaching. Basically, he is letting them know that he has St. Peter’s blessing that he is teaching the same Gospel.