There are several ways. If you are already familiar with how to get to the Contemporary, go that way. When you pass the Contemporary, continue on through the light. You'll pass Space Mountain on your left and a parking lot on your right. When you get to the stop sign, turn right. You'll be right beside the maintenance building for the trains and monorails. Continue straight. You'll pass through one light. DU will be on your right.
If you get off of I-4 at the exit near the Crossroads, you can take CR-535 to Reams Road. Pass the entrance to Disney property across from The Crossroads. Turn left at the next stoplight. You'll see a Shell station on your left. Take CR-535 until you get to Reams Rd. It will take about five minutes. Turn left onto Reams Rd. Follow it until you see the entrance for Disney. DU will be ahead to the left.
You don't need any king of id to take either route. I use them all the time and I don't work for Disney any more. They took away the guard checks for this area about five years ago.
Remember to leave early. I can't stress how important it is to not be late. There were people who were late to my orientation, when I started working for Disney, and they had to leave and come back another day.