I stumbled upon this question which, aside from being in need of some cleaning up, is not "answerable" as much as it's an open community wiki.
How do users convert questions to community wikis?
Regular users cannot convert questions (whole threads in practice) to community wiki. That was once possible, but hasn't been for several years. You can convert your own answer to CW, but that won't make the question CW or the other answers. If you believe a thread should be CW, you have to flag the question and ask the moderators to do it. Just click on the light gray "flag" at the bottom left of the question body, and comment that the Q should be CW and why you think so.