Your best bet for MP matches would be to join an online fleet like GNSF
http://www.globalnavalstrikeforce.com, the Seawolves, or the USVN.
In the general community, there's always hyperlobby
http://hyperfighter.sk/ and gamespy (which I hear is doing pretty well lately).
DW doesn't really support multiplayer campaigns directly, BUT if someone is willing to put in the time and effort to create online campaigns, it can be done. I've been testing one such effort with the help of the CADC and Seawolves/GNSF. Depending on the response I get in the GNSF, I might implement a quarterly or semi-annual war campaign between the task forces there. It's too early to promise anything in that regard, though.