Click the Airport icon in the top right of your screen, and select Join Other Network...:
Enter the following information, as shown in the image below:

Click Join.

Double-click on your hard drive, go to Applications, expand Utilities, and select Key Chain Access. Double-click on Key Chain Access.

Select the System Roots keychain from the list on the upper left side of the Key Chain Access screen.

Scroll down to find UTN-USERFirst-Hardware. Double click UTN-USERFirst-Hardware.

Scroll down to Trust Settings. Expand the Trust Settings and change the Extensible Authentication (EAP) field to Always Trust.

Authenticate with your machine's user name and password. Click OK to allow the changes to the certificate to be made.

You can now close the certificates screen and Keychain Access.
You may be prompted for your User Name and Password, and will need to enter them again. If you would not like to be prompted in the future, leave the Only use this password once box unchecked.
You should now be connected to MWireless.
If you are still unable to connect after following the above instructions, contact the ITS Service Center at 764-HELP.
It may be necessary to turn your Airport off and back on in order to connect the first time.
Make sure you have installed all available driver updates and patches for Mac OS.
If you receive a certificate error on subsequent connection attempts, follow these steps:
If you still have trouble connecting, you may need to reorder your list of preferred networks to give MWireless a higher priority:

Contact the ITS Service Center:
734-764-HELP (764-4357)
4HELP@umich.edu
http://its.umich.edu/help/
M-F, 7 a.m.-6 p.m. (phone and email); Sun, 1-5 p.m. (email)