How to enable TLS1.2 for port 1433
There is this KB article, which lists the required updates you need to install https://support.microsoft.com/en-us/kb/3135244 , which also lists which updates are needed on the client machines trying to connect to a TLS 1.2 enabled SQL Server.

Also, read http://blogs.sqlsentry.com/aaronbertrand/tls-1-2-support-read-first/ , which lists known problems and caveats. It states


  It seems straightforward, but as of today, not all builds will enable you to rush out and convert to TLS 1.2 exclusively