This functionality may have been removed in the much reviled update from 1.2.1 to 1.3. The user -=Someone=- reported the exact same problem on the App Store review board. The only solution I've seen is to foregoe the update.
If you've already updated, you will probably need to roll back to your previous version of Configurator in order to retore the desired functionality. Since the App Store does not support previous versions, you will have to restore your Configurator application and its related data from a personal backup. Based on what I've read, there are two items to restore from backup:
(1) The Configurator application file, located in [your hard drive]/Applications/
(2) The Configurator data folder, located in [your hard drive]/Users/[your user name]/Library/Containers/
Note that your Library folder might be hidden. See https://discussions.apple.com/thread/4380014?start=0&tstart=0 for instructions on how to unhide your Library.
Looks like the option is back with v1.3.1: http://support.apple.com/kb/HT5833
Apple Configurator: Installing profiles on multiple unsupervised iOS devices
Learn how to install a profile on multiple unsupervised devices using Apple Configurator 1.3.1.
In some situations, you may want to install a profile onto multiple iOS devices without supervising them. After completing the initial Prepare process, use the following steps to deploy profiles to multiple unsupervised devices with Apple Configurator 1.3.1.
Hope this helps!