Do you have the tablets drivers installed?
After you have them installed, look at the drivers setup program… there usually have a section for your monitor setup, where you can select single or dual view.
As soon as you do make the change you will only be able to use the top half of the tablet, because of the odd shape of both monitors combined makes a huge number in the width dimension of your total desktop.
I have mine only set up for one monitor for this reason…in the settings you should be able to pick either one monitor or the other, or both at the same time.
hope that helps