first go to AMD.com and download the latest drivers for your specific OS. This will automatically install CCC (catalyst control center). with in CCC you go to "monitor" located on the left side tab, then click on "scaling optioins" this will allow you to adjust the scaling of the screen usually 0% will expand your picture to fit your screen. You will also be able to adjust your resolution and OC your video card if desired.
Actually sorry this didnt work it only returned to full screen because I had unplugged the hdmi cable. On my CCC i do not see any monitor tab I see VGA displays but that doesnt do anything