Create A Wiki Page
Adding and changing content in the Wiki is easy. SteamLab's Wiki uses the same software as Wikipedia, so if you have ever added or changed content there you are all set to go.
You'll need an account on the Wiki. Click on "Request Account" (or in the top right corner of this page) and fill out the form. Use your STEAMLabs Community Slack account name as your wiki account name, that way you'll get Slack notification on changes to Wiki pages you are watching. You will receive an email with a link to confirm your email address. Once the account has been approved you can "Log In"!
New or edit page
Edit any page of the WikI by clicking the "Edit" tab at the top of content area. Create a new page by searching for it's (intended) title. The Search results page will have a "Create the page ..." link if the page does not yet exist. Simply click and you are placed in the editor.
Pages are written in a simple markup language, the important functions of which are available as icons at the top of the edit space. You'll see a brief note about each function if you hover your mouse cursor over the icon.
You can preview your page ("Show preview" at the bottom) and when you are happy with the results go and "Save page". I learned a lot of the markup and formatting rules by placing interesting pages in edit mode and then using "Show preview" to see how markup is turned into pages. Also, new Wiki pages and changes to existing pages that are not flagged "This is a minor edit" will be announced on the SteamLabs Community Slack channel #wiki.
Any new page you create should be connected to the rest of the Wiki, otherwise it can only be reached through a search. Find the page(s) that you want to contain a link to your new page and add links in appropriate places.
To add images to your page, use the "Upload file" in the Tools menu on the left. "Choose File" in the Source File section, and the rest of the form will be filled out for you. The "Destination filename" will be the name by which your image is know on the Wiki, use the "Description" to explain the image. Click "Upload' at the bottom of the form, after that you can use the "Embedded File" icon from the edit tools to add your image to page.
Explore the Tools menu on the left, the "Special pages" section for example has a ListFiles page where you will find the image you uploaded just now (just in case you forgot what it's name). .
This is MediaWiki's main help index, with quick info on editing, and all other things Wiki!
Feel free to ask me (@whome) on Slack!