First I am a total novice. I purchased my first flat screen tv, 37 inch Vizio M series. My old tv plugged into the back of the cable box which has a spot for only a 2 prong plug. My flat screen has a 3 prong plug. How do I connect my flat screen to the cable box. Also when I did look to set up my wireless connection to use the apps, I could not find out how to access the on screen keyboard to put in my wireless security code. Thank you.