If you are looking to use this platform to simply read information about your favorite topic (like a game, movie, or tv show), then just do a web search for a wiki about your topic of interest.
If you want to discuss things with other users on your wiki of interest, then you will need to figure out how to use the discussion tool offered by that wiki. There are several different ways wikis may hold discussions. If you want specifics, please provide the wiki you are interested in.
If you want to contribute to the information on article pages on your wiki of interest, then you should familiarize yourself with the wiki's editing guidelines/rules. If you have specific questions about how to do something, you can ask here. However, there are a lot of help pages you can read at your own convenience.
If you want to create a wiki, see Help:Start a new community. However, the founder is typically the only contributor to a wiki for quite a while since it takes time for other users to find the wiki. So I would suggest getting use to editing before starting a new community.