Board Thread:Support Requests - Designing Your Wikia/@comment-25259230-20140920064102/@comment-15575766-20140920225551

I'm not sure about the second question, but I can answer the first: You'll have to be an admin on the wiki that you want to edit the wordmark on. If you are an admin, go to Special:ThemeDesigner on that wiki. You'll find wordmark and favicon settings under Wordmark.