Thanks for taking the time to make the osu! wiki better!
Anyone is allowed (and encouraged!) to contribute to the osu! wiki.
The osu! wiki is formatted using Markdown (specifically GitHub-Flavoured Markdown (GFM)), a markup language that allows for text to have basic styling.
adam-p's Markdown Cheatsheet is a fantastic tool of reference if you need to quickly learn about or refresh your memory of a Markdown feature.
Since the osu! wiki is managed through this GitHub repository, you'll need some basic knowledge of Git in order to contribute.
Luckily, if you're not willing to get too involved with the technicalities of Git, GitHub provides some on-site tools that can help you easily make changes. The osu! wiki Contribution Guide explains step-by-step how to utilise them in order to make changes to the osu! wiki, assuming that you have no prior knowledge of Git or GitHub.
The Article Styling Criteria (ASC) is a set of standards that must be adhered to for all new and edited articles going forward. Among these are rules regarding project structure, usage of Markdown, formatting, diction and grammar. The ASC is fairly verbose, so please refer to it if you have any specific questions or concerns before asking other contributors of the osu! wiki.