Starting with Domino 4.6, the Model Monitor is installed along with Domino. You can access the Model Monitor using the same credentials used for Domino. By logging in just once, on either platform, you can access both the Model Monitor and Domino. Similarly, logging out of one platform logs you out of both.
Click Model Monitor in the Domino navigation bar to take you the Model Monitor landing page.
Conversely, you can click on Workbench in the Model Monitor navigation bar to take you the Domino landing page.