Can someone please tell me what I have to do to vacate a judgement?

You will have to file in court to prove that some action in the original judgment was not correct ( and why you did not present this evidence at the original trial)

Where you not property served notice, was it not you that owed the money. If you really owe the money, and you were legally served, there is no way to really vacate a judgement

Go to the court where the judgement was issued and tell the clerk you want to file a vacate judgment. But make sure you have good cause to do so, you don't want to look bad in court