I need to purchase a car. I have not used banking or credit for over 10 years. I have a low score. Help!?

I make good money. No debt other than medical (low). Did not pay them due to being ill/overwhelmed. No excuses. Also have IRS bill (auto draw thru work), not on credit report. How do I get back in the system without anyone willing to give me a loan? I don't have a co-signer available to me.