The admissions office is actually quite hard to find! You should first enter the Mayo Building, which is hard to miss. Its the main one with statues on the outside walls, and is next to the Damon parking garage, a great place to park for the day. Go through the front doors of the Mayo building, and follow the signs to "the subway," which is really just a system of underground tunnels connecting all the buildings so that you don't freeze to death in the winter. Once in the subway system, follow the signs towards the Guggenheim building--the Mitchell student center is not "officially" connected by the subway system, but you can get to it. As you follow the signs, you will eventually have to climb up a big flight of stairs. Walk up these, and once at the top talk a right and go through a set of doors. You will soon find a hallway on the right that says the Mitchell Student Center--go down this and the administrative office should be straight ahead.
I hope this helps--let me know if you need more. Good luck, and I am sure you will love it.