If you've just installed Managed Software Center (you may have heard someone in the tech department call it Munki), you may not know how to use it. One major use for MSC is to install software.
You should see a list of approved and pre-packaged software. All the software you see listed you can install by simply clicking Install (no wizards to click through, no icons to drag, no serial numbers to enter).
P.S. Most software will just install, and that's it. For PowerTeacher Gradebook, you'll see a Gradebook First Run.app appear on your desktop once it's installed. Double-click that, and Gradebook will be fully initialized.