Step 1: Pick a target keyword. You need to examine prospect keywords using an SEO tool, like Ubersuggest, Moz SEO tools, etc in order to know if the keyword you are trying to target actually has search volume (are people looking for these words?) and what your competition is for the term (if you're competing against the New York Times, give up now).
Step 2: Make sure your site is equipped to compete for the keyword. Pick keywords that are consistent with your site niche and make sure that your meta description is current with your site goals and plans.
Step 3: Write the article. Include the target keyword in the title of your article, but make sure that the article title is as short as possible while being clear enough for humans to understand. Mention the keyword in your article as appropriate. Err on the side of human understanding - your goal is to assist humans, not robots. Humans have money.
Step 4: Make an appropriate image for your article, and put the keyword in the image's alt text. Make sure the file name for the image is descriptive, concise, and fits the article that you are writing.
Step 5: Take your article text and image, and put it through a SEO checker.
Step 6: Publish the article. Check to make sure that your url includes the title for the article.