Specify which omeka-s site will use which iiif manifest

Do I use config.json to tell omeka-s to only use a specific manifest on a specific site, and can anyone give me an example of what that looks like? Also where do I store a manifest.json (or do I name it info.json)

Do I configure any of this in the module configuration settings within the omeka-s admin pages?

Thanks!

so it looks to me like I can make my own context.json, and then point to it in iiifmanifest.php - however it seems that no matter what change I make in the iiif server - even on the configuration page in Omeka-s modules, Universal Viewer disappears on my item pages. Is there some sort of clear cache, or reset UV that I have to do to ensure iiif server module changes do not break UV?