To create a new page on Wikia, type in the name of the article.
For mun, it should be the same as your mun name. Then, at the bottom of it, place [ [Category:Muns] ], without the spaces. Fill out whatever is necessary for you on your page.
For a character, it should be named the same as your character journal. All underscores should be represented as dashes. At the bottom, place [ [:Category:Characters] ], without the spaces. Then, go to the category, hit edit and scroll down to where that character's game is located. If their name isn't already listed, type ==='character name'=== under the game. Then add the character's article to it.
If you create a Greatest Hits page, name it appropriately, according to what happened. At the bottom, place [ [Category:Greatest Hits] ], without the spaces.