First, the technical details:
Go either to Posts -> Add New, or New -> Post. Both options will lead you to the editor page.
In the space under Add New Post should be where you place the title of your post. If linking to an article, simply indicate the source and title; otherwise, use your own judgment to come up with a title. Keep it simple and easy to identify.
The bulk of the post editing will be in the large blank space below. The toolbar is fairly standard, so I expect that all of you should be able to figure it out on your own. Of special note is the ability to add media; to make your post more readable, minimise the addition of media (don’t make it a photo gallery).
Links are particularly useful in an online format like this, especially where some claims may not be obviously true. If your post is centered around some online resource (as most will be), start the post with the link to that article or other resource. For greater readability, you may want to make the links part of your text instead of distinctly typed-out URLs.
Those of you that are more familiar with blogging sites or are feeling more adventurous may want to play around with different post formats, but the standard format works fine for most purposes as it is.
For each post, do also scroll down and check off the appopriate category of the post (on the sidebar to the right, below the list of formats), and tag the post for relevant ideas. This will be important later on when you may need to search for posts.
For resources being linked to, you would want to copy-and-paste it in your post – the picture itself for pictures; embedded video, an image still or just a link for videos; and a short excerpt for text articles, with one key image at most.
More important than the link is your own response to it. For each post made, provide a 1-2 paragraph synopsis or summary for articles linked to; if linking to more than one article (e.g. 2 different articles with opposing views on the same idea or event) then some comparison would be useful. For pictures, a short caption followed by some key ideas and questions would be useful.
Those who create a post will also have to post 2 comments on their own post. Ideally, this should be discussion starters – some form of question(s) or contestable claim (with elaboration) would probably be the most useful.
You are of course also free to simply write a post, instead of responding to an article. This could take many forms, e.g. a response to an essay question, or perhaps just a quotation; a broad reaction to current affairs and issues; or examining a concept in more detail.
Most posts will be links of some sort, though, so it is important to reiterate that it is your response to those ideas that is important. There is relatively little value in simply copying and pasting a link; the one who posts should provide a basis for discussion through a short summary and some questions raised by the resource.