I am getting the TCL 6. Series QLED TV.

If you Look on YouTube it Tells you to Bring Up on YouTube HDR Movie Content so the TV goes into HDR Mode.
Then do the Picture Settings for that.

Then Bring Up Dolby Vision Content so it goes into Dolby Vision Mode.
Then do the Settings for this.

But how do I Pull Up HDR Content and Dolby Content on YouTube?

 

Bypass YouTube and go straight to the source hope this helps
https://www.manualslib.com/manual/1608104/Tcl-Roku-Tv-6-Series.html

 

Thank you but it just gives the TV Instruction Book.

I need to Play HDR Video and Doby Vision Video to enter the Modes.