Content and SEO are two different things. You use SEO to optimize your content and your site (or your parked domain, if they allow it).
If you put an article on your site that is also on many other sites, you are unlikely to get much benefit. But if you optimize the page that the article is on, you may get more benefit than you expect, or that many will tell you to expect.
Let me put it this way: if your copy of duplicated content is better optimized than all the others, you should get some benefit from your SEO work on the page.
People can ask for help and advice, but I suggest you consider doing some TESTING. Try some things out for yourself and see what works and what doesn't. You may find that some things that people say work, doesn't for you, and things that many people say don't work, actually do better than you would expect.