We will contact using Skype. If you don't have Skype, download it, it's free
i would not recommend using skype, as the delay on voice is terrible, and it's an awful platform for creating a team communication environment. most teams use Mumble for communication, since the delay is minimal, and the server-based connection system is much better for a team environment (skype is more suitable for 1 to 1 call style communication.)
you would have to rent a mumble server for this, but most server providers give a free mumble server with a gameserver rental, so it shouldnt be an issue