Hi and welcome.
Winnebago makes many different motorhomes with many different entertainment systems. If you can detail what you have with names and photos then many of us can help provide into. Otherwise you'll have to wait until a 2017 Vista 35LX (It's LX not XL) owner comes along.
I looked up your Operator's Manual. Section 8 is for Entertainment System and it has all the info on how things work.
Look like you have what Winnie owners call a "BOMB" - short for Box of many buttons.
Here's a link to your Operator's Manual. Just click on the Entertainment in the side bookmarks of the PDF:
https://www.winnebago.com/Admin/Publ...16Vista_LX.pdf
It shows an optional DVD player in your "radio/CD" player and sometimes the radio in the dash has a CD/DVD slot. When the vehicle is in Park and the Parking Brake set it will show video from one (or both) of those DVD players.
To attach a Blueray or DVD player separately I think you connect it to an AUX input on the back of the BOMB - but I have no experience with the BOMB so others will have to help you with that.
Winnebago likes to make their own TV mounts in house and they are generally over engineered metal plates. You have to get behind the wall or cabinet they are mounted to and then unscrew the mounting plate before you can move the TV.