Hello! I'm quite surprised you'd ask me such questions, but let me try to answer that.
If you ask me for an advice, I would recommend you to understand the policies and guidelines for the Wiki you want to contribute to. Although all Wikis are supposed to follow the same ToS, each Wiki may have their own rules, so please keep that in mind! Also, never violate the Wiki's rules at any circumstances!
From that, if you don't know what to contribute, you can ask the staff members! I'm sure they have a ton of work, so you can lend them a hand!
Try to familiar yourself with source editing style as well, I'm sure if you learn slowly but sure, you will manage at the end!