If you're over 25 years old, you don't need a certificate from an adult drivers ed course. Just make an appointment for a drivers license test at the DPS. There, you will take your written licensing exam, and vision and hearing tests, before getting behind the wheel for your road test.
An easy way to bypass the licensing exam, however, is to take an adult drivers ed course anyway. Your final exam for the course replaces your written exam at the DPS, making it much easier to pass.