The forum open-graph images are to be uploaded via FTP. For threads, admins and moderators can upload images as open-graph images.
To show ads only on the homepage can vary based on how you wish to show them – using an ad manager addon or by modifying the template. Let me share both.
Recommend my existing vBulletin clients to move over to XenForo. Here is a list of my clients forums that were in vBulletin and has moved over to XenForo
XenForo add-on installation guide with screenshots intended for new XenForo webmasters who are just starting out with XenForo.
The complete step by step guide with pictures of every step to help install XenForo locally on localhost running on XAMPP.