The Database Compare Window allows you to see the differences between your Model and the Database at all times. It contains the same pages as the Database Compare Wizard but is "modeless". i.e. you can work on your Model while its displayed.
If you want to export a difference to the database, select the compare item and click on the solid blue arrow that points to the right. To make the corresponding change in the database, click on the navigate forward button at the top of the page til you get to the Generate Script page. This page allows you to execute or "Save to File" the database commands that will effect your changes in the database.
To create these commands, ModelRight 4.1 keeps an internal list of the changes that you have made. Once you have executed or saved these commands, you should select the "Commit and Return" toolbar button 
, to return to the Compare page and to indicate to ModelRight 4.1 that it can reset this internal list of changes - so it won't continue to create these same commands.
As with any other ModelRight 4.1 window, you can dock or undock this window (by dragging the tab). You can Auto-Hide it (by selecting the pushpin on the window's border). Or you can change the order in which its listed (by dragging the tab to another tab position).