Praise be to Allah.
You must hasten to repent to Allaah from this evil action and major sin, and to ask for forgiveness and do a lot of righteous deeds so that Allaah may forgive you. With regard to the girl with whom you committed zina, it is not permissible for you to marry her unless you both repent to Allaah, it is clear that she is not pregnant and her legal guardian consents to your marrying her. Otherwise, look for a chaste girl and remember how grave your sin was. May Allaah forgive us and you.