An article is a post that is much lengthier as compared to a blog post. But, if you look it on a broader level the things that you will need to optimize them will be more or less the same.
Here are few tips for optimizing them:
1. Post title and meta title: Post title is the title that your audience see while meta title is the title that the search engine sees. You will need to define the meta title in your SEO setting, or your post title will act like the meta title. You need to add keywords to both of these titles.
P.S: Try to limit the post title to 50-60 characters as Google cuts down it after 44-45 character limit.
2.) Meta Description: The meta description is the small description of your article that Google displays just below your link in the search results. All SEO plug-in allows you to add meta description to your article. It should be keyword-rich, limited to about 150 characters and good enough that audience clicks on it.
3.) Image alt text: Add keyword specific alternate text to your images. You can get traffic from good pictures as it will be placed higher in the search rankings.
4.) Interlinking: Do not forget to add links of your older posts(wherever possible and appropriate) in the new articles. This way people will dwell more on your website, and it will prevent bounce rates. When you do the interlinking, you are required to add a title and a URL( relevant to the old post that you are linking to) . You should add the root keyword to the title tag relative to the post that you is being linked.