Well, the ONLY way you can get 2 different channels at the same time on your TV would be if you had TWO tuners in it.
Now you do have the DIGITAL TUNER --That works, but the problem is They turned off the ANALOG channels, so your analog signal doesn't even exist right now. That was your second tuner, now it's obsolete !
So, now you are forced to use one of your Video inputs for the second picture.
However, if you look around at some of your electronic stores, you may find a Digital to "Video output" reciever -- That will become your 2nd tuner and it connects to the Video input on your TV set, so the TV can fulfill it's need for one video input being used, and using the Digital tuner as another input.
I'm pretty sure you can search for a "Digital converter box" online. Try "dvb-t tuner box"
and see what comes up there.
As for CNN and any comments I made about that, CNN isn't FREE over the air -- we have to buy satellite or Cable services to even get it.
The only channels we get over the air is NBC, ABC, CBS, CW and PBS and some other lame channel that I don't care about.
If you get CNN without a cable or satellite, you are very fortunate.
The BEST way to explain your situation is you do need to use the Digital tuner built into your TV set along with another DIGITAL tuner that can be plugged into one of your Video inputs. When you press the PIP button, you can select different INPUTS by using your Input button on your remote. It may be labled source or input, but it's the same button you use to choose your DVD player when you want to watch that.
If you still have your instruction book for your TV set, there is a chapter that tells you which buttons you should use.
If you have any questions, just ask