I am an attorney and I am licensed to practice in Washington state. However, do not take this as creating an attorney-client relationship. Here is my opinion.
You said that an address changed, which I take to be your address. You can call the court in the county where you were charged. Ask for the criminal case department. They can tell you how to put in a proper change of address.
Many counties in Washington have diversion or deferred prosecution programs that allow people like you to avoid a criminal conviction. It may involve having to go to an anti-shoplifting class, paying program fees, and performing community service, but if you are admitted to that kind of program and complete it successfully, the criminal case is dismissed and you have no criminal record.
Diversion is not automatic. You need to consult an attorney. If neither you nor your parents can afford a privately hired attorney you need to tell the court that you can’t afford an attorney and ask that one be appointed for you. That is not free either. There may be a payback obligation, but that is something that can usually be handled over time so don’t worry about that now.
Do not depend on court staff, judges, or prosecutors to give you advice on how to handle this. It is not their job to protect your interests. You need to have the advice of an attorney in your specific area to guide you through this.
Do not go to the store or talk to the store manager. It is out of their hands now, anyway. In fact, stay away from the store altogether. You were probably given a store ban and if you go back there you can be arrested for criminal trespass.

