Hi Sharron -
There may be a couple of different locations for a "heading" in Canvas.
Some instructors use Assignment groups to organize content. These can be labeled (and weighted, if you're interested) however you'd like. How do I add an assignment group in a course? How do I move or reorder an assignment group?
Some instructors use Modules in combination with Assignment groups to further organize course activities. How do I add a module? Within a module, there is an option to create a Text Header. https://community.canvaslms.com/docs/DOC-26560-how-do-i-add-a-text-header-as-a-module-item?sr=search... I like this feature a lot, as it helps clarify each module's progression.
If I've misunderstood your question, I'm sorry. Please share more information about your question and let me know how I can be of further help! 
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