In NC I always went to the nearest IRS office the first time I paid it. After the first time on each truck the IRS will send you a notice. You can also download a form from the IRS and send it in with a check. I went myself so I could have a stamped paid receipt.
If you are buying the truck from a private party see if they have paid it for the year. It would carry over to you so you would not have to pay it for this year.