If you've installed Workbench to hard disk correctly via the Installer diskette then you should have a 'Prefs' drawer on your boot partition (normally DH0). Inside there are programs to personalise your Workbench. One such program is called Overscan ; you can move the screen location around with that and also stretch it out to perfectly fill your display. If you're happy with the changes you should click the Save button. If your Workbench is installed correctly, then the next time you boot it will remember the screen location.
