1. These forums were to support XNA.. I dont think anyone here knows about how to use OAuth
2. These forums are mostly dead... the handful of people left are just shipping the final few XBLIG
Most things to do with xbox auth would likely have to come through a partner program e.g. these are the current developer programs http://www.xbox.com/en-US/developers/home
There used to be a partner program for xbox.com but I think it has been discontinued - you can try in the xbox.com forum for that information
and of course OAuth docs are here https://msdn.microsoft.com/en-us/library/hh243647.aspx - that should work for all MSA accounts I am not sure of what you need to be whitelisted for.
Sorry we cant be more help