In order to change the resolution that the software runs your experiment in, you would need to change the resolution parameters within your experiment's style file (*.drt) . If you do not have a .drt file within the same directory that your experiment is located at, then it means you're using the default style file for your experiment.
More information on style files can be found here:
http://www.empirisoft.com/directrt/h...yle_editor.htm
Once you open up the style file that your experiment is using, you will want to navigate to the 'Options' button, and click it. A new window will open.
Within this window you will be able to specify the screen size that you would like your experiment to run at.
More information on changing these values can be found here:
http://www.empirisoft.com/directrt/h...creen_size.htm