How to contribute the wiki
see the tutorial "Adding or editing wiki pages".
The page is Markdown-enabled by default. Please see here for more information on Markdown syntax. You can also access some commonly used syntax at the top toolbar of the editor:
Your picture has to be inserted using its URL. If the picture is on your local computer, you need to add it to this repository to get an URL. First, go to this repository's code section, then create a folder named your page title inside the "pictures" subfolder and upload your pictures to that folder. Git doesn't allow you to push an empty folder, but you can first create a temp file to create the subfolder. See here for details.
Then you can get a URL for the picture you just upload.
If you have created a new page, please also update the "Table of Content" page to include your new page. Put your page into appropriate sections or subsections. Create a new section or subsection if needed.