File a petition for expungement
Not all records can be expunged. Convictions can NOT be expunged unless the conviction is for a summary offense and it has been at least five years from the date of the conviction. As for the filing of the petition, make sure that it complies with all the local rules and includes all the necessary information.
Go to court and litigate the motion
Assuming you don't have a right to expungement you may have to go to court to litigate the issue. Explain to the judge why you need your record expunged and hopefully the judge grants your motion.
Get certified copies of your expungement order
After you win your motion you will have to get certified copies of the order and serve it on each agency in the state that keeps a copy of your record. If you don't do this your record will not get expunged. Good luck.