Clarify HDMI connection instructions in documentation

[magbaeta]

Some users have mistakenly connected the HDMI cable and experienced a "no video source" issue.
It is not explicitly stated in the documentation that the HDMI cable should be plugged into the graphics card rather than the top port.

Maybe it would be helpful to update the Getting Started documentation section to clearly specify the correct HDMI port for display output. Like adding a note that the HDMI cable must be connected to the graphics card, not the top port, to ensure proper display output.