That's because phoning British Rail to find times of return trains can be a frustrating experience. To get the local train, change at Birmingham New street. They leave roughly every 15 minutes for most of the day. There's an information desk on the main concourse near the platform. If you have a through ticket to University it saves going out through the ticket barrier then coming back in again.
University is the second stop.
It takes about 7 minutes to get there. It's a 5 to 10 minute walk to the School of Computer Science. Come out of the University station. Turn left again, and cross over the railway line and canal into the University grounds. You should then be able to see the big clock tower.