How the F%#$ do i pay for a collection!? (credit)?

I am trying to join the airforce, they ran my credit, and the only thing that shows up on my credit report is a little piss ant 67 dollars. I can't seem how to figure out where it came from. I have the Agency/Client serial number and it shows me the amount/bal. It sais unpaid. I just need to know how i can pay this off. Thanks in Advance.