For starters pay off all of your debt that you owe or whatever you have on there. Call the people you owe and tell them to take it off your credit report and you'll pay it. I'm not an expert but, I had no credit about 3 months ago and my SS was used to open up a store card and used $400 on the spot. I got a call from collection agency and didn't really care and told them it wasn't me. I didn't realize how bad it had gotten until I was looking to buy a car for work. I spoke to someone about it and they told me to pay it and then dispute it. Just by paying it brought my credit up 40 points. I never had a credit card. I ended up getting co-signer and got approved for a car loan. My plan now is to get a secure card and make those monthly payments on time. Go to CreditKarma.Com they have a lot of useful information. Like don't go over like 25% off your limit and make full payments on time etc etc..
You paid it just to get a car loan? That's $400 out of YOUR pocket because someone committed identity theft.
If anyone runs into this, inform the collection agency that they MUST provide written proof that it was you within 30 days under the Federal Fair Debt Collection Practices Act of 1977. If they do not provide written proof, they are required to stop contacting you and inform the credit agencies that it's not you. You should also write a certified letter to the 3 credit bureaus requesting the same.