If the picture on your screen doesn't quite fit, or there are bits cut off, there's a really easy way to adjust it!
From the desktop, click the Apps icon:
Click on the Tools tab:
Then click on the Settings Icon:
Click on the display Icon:
From here you have the option to change your screen resolution, or if you just want to make a small adjustment click Overscan:
Move the slider and the image on your screen will start to shrink. When you're happy with the picture, click Apply Changes. If you want to make more detailed adjustments, click advanced to control every side individually:
Once you have finished, simply click the X in the top right of the window. You must reboot for the changes to take effect: