I’d hoped to have some video that would help you post to a WordPress site in case you haven’t before, but for now you’ll have to figure it out. The first thing you need to do is to register on the site. Here’s some general information about registering.
You’ll need to log into the site from the home pages (right hand menu item, under “Meta”).
And then you just click on “New Post” from the top banner on the right of the page.
For the distinction between “categories” and “tags,” see this. There are categories set up for all the assignments. Please use categories and tags for all your posts.