I couldn’t quite grasp how selecting the character’s body FIRST then the armature works when parenting, but then selecting the bone FIRST then the TV head works as well.
My guess is because of different functions, first one is Armature with weights, and the next one is Bones. It might be how Blender works but I’m not getting the logic why the selection order is different for both cases.
Character first then the bones/armature.
Same with the head. Head selected then the armature. (having selected the correct bone in the armature as in the lecture)
What you do is to connect vertices as a child to a bone as a parent.
But connecting a vertice to a bone is a cumbersome job.
That’s why we use weightpainting (blue to red) to paint the vertex relation to a bone.
And to be even faster you can use automatic weightpainting. But then the logic of Blender algorithms will do it for you. And sometimes you need to fiddle with the outcome by hand.
Another way to connect vertices to a bone is using just the object. Then All vertices in the mesh of the object become red, without weightpainting.
red means 100% under the control of the bone, and blue means 0 (not influenced by the bone).
If you are experimenting, be sure you reset sometimes the weight painted maps.