First things first
If you aren't familiar with mediawiki syntax, check out this [tutorial] from Wikieducator. This covers basic wiki commands and style.
You should also create your user profile, making sure to add [[Category:User]] at the bottom. Generally, every time you make a new page, you should categorize it. A list of existing categories can be found [here], but don't be afraid to create your own if you feel the need.
You may also want to create a subpage of your user page just for experimenting and playing with syntax, so that you can try out new things without affecting pages in the wiki. For example, you can create a Sandbox subpage of your user page by putting [[User:USERNAME/Sandbox]] in your profile.