You need to become extremely familiar with RCW 9.96.060, or retain an attorney experienced in these matters. You will learn that you cannot get a conviction expunged, but you may be able to have it vacated if you have been off probation for at least three years (five years if it was a domestic violence offense), and have had not subsequent criminal history or pending criminal charges.
A person can have a conviction expunged without making an appearance. If the offense is a qualifying offense and and enough time has passed without the offender obtaining new convictions, you can hire an attorney to prepare a motion and submit the paperwork to the Court. Make sure you hire someone who has experience making motions to expunge, or vacate convictions.