Hi Kirsten Grant,
Thank you for reading my article and I am very pleased to say it was helpful. :)
As to your question:
It takes time to tweak an existing article to make it optimized.
I usually recommend doing an analysis first, where you check who's on top for your keywords, how many keywords they rank for, how many backlinks they have, how long their content is , etc.
Then, do keyword research. Analyse which keywords your competitors rank, but you don't. Rewrite your existing content or simply add more optimized content to an existing post.
Wait for a few weeks and check your rankings.
This should help. :)