The dedicated server tool should now be visible from the tools menu in steam. For instructions on how to set up a dedicated server, there is a guide at: http://steamcommunity.com/sharedfiles/filedetails/?id=907906289
For your launched dedicated server to work, a valid configuration is mandatory, default setup will not work.
We are currently working through lots of issues with dedicated servers and so still recommend most players continue to play regular P2P multiplayer whilst the issues are ironed out. In particular clients may experience black screens when attempting to join servers that are not correctly configured and player counts are not currently available.
As always, please continue to post your bug reports and feedback in the Discussions area of the Community Hub