This one is pretty simple. Just play your best and try to finish dynamic goals and goals your head coach gives you. I'm not 100% sure, but I think there is a certain date scripted into the game that your player cannot start prior to. I didn't get my first start until late December. Eventually with solid play, you will become a starter. You'll know you're close when you get conversation cutscenes with the GM and head coach talking about your minutes increasing and eventual imminent start.