You need to either file a motion or get a stipulation to set aside default and vacate default judgment. Most likely, you will need an attorney to do this because there are no "forms" that you can just fill out and file.
In California, a defendant who has been defaulted by failure to respond to a summons and complaint might have an opportunity to set aside the default based upon Code of Civil Procedure § 473.5.
“When service of a summons has not resulted in actual notice to a party in time to defend the action and a default or default judgment has been entered against him or her in the action, he or she may serve and file a notice of motion to set aside the default or default judgment and for leave to defend the action.” (California Code of Civil Procedure § 473.5(a). )
The motion must be served within the earlier of two years after entry of a default judgment against him or her; or 180 days after service on him or her of a written notice that the default or default judgment has been entered.
The moving party should submit a sworn declaration as to when he or she first learned of this action, whether he or she was ever served with the summons or complaint in the action, and whether he or she ever received notice of entry of default.
“A notice of motion to set aside a default or default judgment and for leave to defend the action shall designate as the time for making the motion a date prescribed by subdivision (b) of Section 1005, and it shall be accompanied by an affidavit showing under oath that the party's lack of actual notice in time to defend the action was not caused by his or her avoidance of service or inexcusable neglect. The party shall serve and file with the notice a copy of the answer, motion, or other pleading proposed to be filed in the action.” (California Code of Civil Procedure § 473.5(b).)
The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author (who is only admitted to practice law in the State of California). For specific advice about your particular situation, consult your own attorney.
you can try and get the lawyer who obtained the judgment to stipulate to setting it aside. Alternatively, you can file a motion to set aside the judgment pursuant to CCP 473.5 if it is applicable under the circumstances. I just prevailed on a motion pursuant to this statute yesterday.
Contact a local attorney who handles consumer issues and get some advice from them