plug both monitors to your machine and boot
you should have catalyst control center installed if not install it
open catalyst control center should look like this
under the desktop management section select creating and arranging displays
you should see both of your monitors there and what type and make they are
make sure both are enabled and if one is not right click the disabled monitor and enable it
after enabling it you should have an image on both monitors
still on the catalyst control center arrange the displays as they physically appear on your desk
right monitor should be on the right and so on