Most institutions require that you apply for the WUE rate BEFORE you begin classes. You can contact the admissions office to see if it is possible, but it is highly unlikely that they will award the WUE tuition retroactively. In addition, make sure that if you were awarded the WUE discounted rate that you have it in writing from your enrolling institution.
I just learned about WUE and already started classes. Can I apply for the WUE tuition rate after I’ve enrolled?
Western Undergraduate Exchange (WUE)