You must copy the scripts, and then configure the module.
Steps
extract the content of MDBRHistogram_vxxx.zip file in a folder; you will see
copy MDBRHistogram.jsx (or the binary version MDBRHistogram.jsxbin) and the necessary script md5.jsx to the scripts location. To locate StatupScripts, open Bridge Preferences and click on the reveal button.
Scripts location usually are on Windows in "%appdata%\Adobe\Bridge CS5.1\Startup Scripts" while on Mac in library/application support/Adobe/scripts.
when Bridge starts, answer Yes to register both scripts.
restart Bridge.
the first time you launch Bridge, go to the Preferences panel and then to the Histogram preferences tab; you must press "Reset to defaults" to confirm path and startup values. At the end click "Ok".
to test the module, go back to main Bridge window; to enable Histogram panel select the menu item Tools->Histograms->Show
An histogram will show when you select an image. Probably Photoshop will open.