The most important SEO things to consider are:
1. The Title Tag. This is usually the Article title. Keywords here will be considered the most important.
2. The Header 1 Tag. Keywords in the Header 1 tag are considered above other page content.
3. The Header 2-6 Tags. Keywords in the sub header tags are considered important for indexing.
4. Paragraphs. Keywords in the text of paragraphs are considered when indexing a page, but not as much as the header or title tags.