Where can I store the pictures I want to include in the articles?
As a matter of fact, you can store pictures right here on the wiki. If you'll look at the left-hand side of the page, under the search box, there's a "Toolbox" section. Just click on "Upload file" and you'll be taken to a page where you can, well, upload files.
After that, to use the image on a page, just use the wiki's image tag, which is [[Image:(filename)]]. For instance, typing "[[Image:Ffh.JPG]]" would display this image: