CSS for Highlighting Text

you could do it in a code block. add a code block and use the following HTML / Style

<div style="background-color:#CB4342; color:white; font-weight:bold; padding:0.5rem 1.5rem; border-radius:4px; display:inline-block; font-size:large;">
  STEP 1
</div>

if you're going to use this in more than one place, then add the style bit as a class to the Custom CSS in your site (go to Design from the main menu of the editor) like this

.redLabel {
	background-color:#CB4342; 
	color:white; 
	font-weight:bold; 
	padding:0.5rem 1.5rem; 
	border-radius:4px; 
	display:inline-block; 
	font-size:large;
}

and then in your code blocks use this class like this

<div class="redLabel">Step 1</div>