What happened before that? Why did you change the starter ? You probably messed something up during installation (happens all the time). Which means that its fixable. Go through exactly what you did in your mind. Its best to stand in front of the car while you do this. Be slow and methodical, and be zen about it. Don't worry....its probably something really minor that you'll laugh about when you discover.
Basically, make sure everything electrical is connected, your gear shift is in park, and all of your fuses are working. Make sure your fusible link is properly connected. Check your battery connections - you probably unhooked them for the installation. Then check if all your relays are working. Then download the bentley manual and check the starter troubleshooting list.
Its best to get a good nights sleep before you start looking at this again.