Board Thread:Support Requests - Getting Technical/@comment-4611027-20161015151637

I'm an admin on the Peppa Pig Fanon Wiki. I can edit MediaWiki pages, but I can't edit "MediaWiki:Chat-start-a-chat". I want to change it from "Enter the Peppaverse" to "Join the Chat" because the "Peppaverse" name for the chat sounds unfitting, but I can't have permission to edit it. So how can I edit it? 