You can try to reset your tablet by holding down the power button for a few seconds. It will prompt you whether or not you would like to turn off the device and if you can select the off button, this will power down your device.
If your tablet still does not respond your tablet may need to be reset using the factory reset button located on the back. You can press this button with an unbent paperclip. Hold for a few seconds and then try to turn the tablet on again.
If your screen still does not work you may have a broken digitizer. If this is the case you will need to replace the digitizer. This can be done by following the digitizer replacement guide. (A link to this page will be added later)