Uploading pictures is easy, there's a dedicated upload tool in the toolbox, which ^ can see in the sidebar. Since we use the newer WikiEditor tool, over the original base MediaWiki editing tools, ^ will be able to find the tool which inserts the code for images on the WikiEditor toolbar.
As for editing, < recommends you check out the official MediaWiki help pages. Fifo also made a sandbox page, if ^ wants to test out how things work. ^ could also try making a user page based off <'s, or any other active contributor's, as they tend to use quite a bit of the basic MediaWiki code.
If ^ still isn't comfortable, ^ could always write up ^'s edits on a text document, we can always just take the text from such a document, and work it into the relevant articles.