If you want to learn how to write a feature article, you're going to need to learn, first and foremost, how to catch a reader's attention. Studies have shown that newspaper and magazine readers decide whether or not they're interested in an article within the first few sentences, so if you don't have their attention right away you're never going to get it.
There are a lot of different ways to open up an article, so try out different techniques, but whatever you do, don't start out with the basic facts of a story unless they're particularly shocking or unique. Questions are often good starters since they get readers involved and invested with the article, while quotations or observations that are particularly arresting are great ways to kick things off.
The next step in learning how to write a feature article is learning how to keep your audience's attention once you've got it. Take a look at some of the excellent articles you've read in the past, especially from major publications like The New Yorker or Esquire.
If you're looking to know how to write a feature article it's good to take a look at how the best of the best do it. Across the board you'll notice that they grab your attention from the outset and never, ever let go. These articles move along at a fast pace, plugging in layers of interesting commentary and provocative facts without stopping to take a breath, since if you stop to take a breath you're going to lose your audience. Keep the pace quick and the writing tight and you'll be able to carry all of your readers along with you.
One problem some writers have when figuring out how to write a feature article is that they forget to learn how to research their stories. Writing a feature article isn't like writing a small article or a story since the research and sources you use have to be better and more plentiful.
One source is hardly ever going to do, and it's good practice to gather more information than you'll actually need to assure that you know everything that's relevant to the topic. You should have one or two primary sources; accounts of people who have been directly involved with the topic, along with some first-hand experience, if possible. Then back up that information with other sources to fill in the gaps in your knowledge before putting it all together in your article.