USMT does not provide any GUI for its three command-line tools. Additionally, USMT command-line input can be very complex. There are many third-party GUI frontends available on the Internet, and also commercial products incorporating the USMT engine. I will pick some of the GUI frontends you should have a closer look at:
USMTGUI (http://usmtgui.ehler.dk/): A very powerful one window GUI for USMT. Newer versions of USMTGUI are now Donation ware. Depending how much you donate, you will get the basic or the pro version. The new pro version is now also able to handle all advanced USMT features for offline migration.
Workstation Migration Assistant (http://dcunningham.net/applications/workstation-migration-assistant/ ): This nice looking UI was written by Dan Cunningham and is now open source, and the source code is available on GitHub. It is highly customizable so you can adapt it to your needs.