As you may already know, Fedora Magazine is a Wordpress site, making article writing really easy.
How to create a post to the Fedora Magazine
Once you login to the site using your FAS openid FASNAME.id.fedoraproject.org, go to the dashboard, and under posts go to add new. Choose a title that best describes your article. Try to keep it small. It is highly recommended to add a picture that is relevant along your article (click on the media button and choose your picture). If the photo has not been already uploaded, click on the Media Button and upload it yourself. Choose the picture with the best resolution, yet also fits your needs. After importing it in your post, drag and drop it in the best spot on your article and use the align left/center/right buttons to reposition it in the best spot. If you can't find a picture for your article, you could use the Fedora Infinity logo in a small corner. (Not always recommended)
Categorize your article. Choose a category that best describes your post (eg. General News). It is not wise to add your article in many categories, nor to create a new category. You can also add tags in your article (like F20), but don't add too many!
Don't forget to add a featured image in your post. The featured image is displayed on the front page of the magazine. If you can't find one, you can add the fedora infinity logo.
There is actually no minimum word amount, but you should fully cover the subject you are writing about. If you can't, you can add a link at the bottom of your article mentioning that more information can be found at that link. You can add links with the add link button on the editor (you cannot just copy-paste it into your post).
At the end, double check your article for spelling errors. If you are not a native speaker, or if you are not sure about something, you can change your article's status, from "pitch" to "pending review", and save it, not publish it. That way an editor or an administrator will take a look at, make any corrections and publish it for you. (Don't worry, the author of the article will be your name either way)
Before posting your article check your permalink, that the correct category is added, a featured photo has been set and the article's visibility (public).
Below are screenshots of the process on where to click and going over the text above.