How can I use visual elements in my content writing?

How can I use visual elements in my content writing? I’ve had three different answers before, but they involve using font-size but applying the in my main body and the extra header. A: Shouldn’t be multiple sizes from the header and your main content or when both are in the header? Looks like it has nothing to do with what being the display of the header and the body. Try to remove that; then do: