Login to VC- Select Host-then in Right Pane select configuration TAB-Go to Authentication Services(Software) -Properties[right corner top tab] -Select Directory service type, and give ur domain name to add !! -next next done.
By default ESX Admin group form AD[if exist in AD, else create this group or replace entry in advanced setting-config] is part of root cred. @Host.
Microsoft has ended support for Windows Server 2012R2. This means not only an end to features and bug fixes, but an end to security patches as well. Rather than building a new server from scratch, there is the option for an in-place upgrade.