These are links to pages on the MediaWiki site that discuss creating pages, formatting, adding images, etc.
A 15min YouTube video on MediaWiki markup basics
Files up 100MB can be uploaded either locally (from your computer) or from a URL. Just click "Upload FIle" above in the menu bar.
Currently, the site supports uploading the following types of files: 'png', 'gif', 'jpg', 'jpeg', 'doc', 'xls', 'mpp', 'pdf', 'ppt', 'tiff', 'bmp', 'docx', 'xlsx', 'pptx', 'ps', 'mp3', 'mp4', 'ogg', 'ogv', '.ogx', '.oga', '.spx', 'flac'.
For large files, such as audio and video work examples, it is recommended that you embed a file from another source, such as Vimeo, YouTube, Sound Cloud, etc.