You should apply for graduation when you’re at senior status (96 units or more). You can either visit the Student Enrollment Services Graduation Center or go to your Degree Evaluation screen to begin the graduation process.
Before you register for your last semester, you must see your adviser to fill out your CORE and major/minor checklists that will be submitted to CASA and the Graduation Center. This is a very important step, especially if you have course substitutions that your adviser has approved.
It’s important to apply to graduate as early as you can, so there aren’t any last-minute issues.