After you receive your assignment letter, you must either call the school or login to Apply.LAUSD. Mail paper applications before the application deadline to: Los Angeles Unified School District Unified Enrollment P.O. Box 513307.Los Angeles, CA 90051. You must submit a Statement of Intent to Register (SIR) to officially accept your admission offer. The online application is available at Cal State Apply. Follow the posted deadlines to submit your application and supporting documents. That's just a welcome to the program letter.