It's a good idea to use relevant keywords in your article body text. When writing or editing your text, ask yourself what words your visitors would use when searching for the content you offer? Try to anticipate the different search terms, synonyms, and abbreviations that different types of visitors would use.
Tip
If you're stuck for keyword inspiration, you should definitely consider using one of the many online tools available. The Google Adwords Keyword Tool is an excellent example; you'll find it at https://adwords.google.com/select/KeywordToolExternal.
Make sure you use keywords and synonyms throughout the article, but don't stuff your article with keywords just to get search engines to pick up your article—their robots won't be amused, and neither will your flesh-and-blood visitors.