Hopefully we can make this process easier in the future, but for now, here’s some instructions to help you:

In order to be able to host a game successfully, TCP Port 7777 must be open in the ​*host*​. If the clients trying to connect to the host are stuck in the connecting screen forever, or get a timeout error, the ​*host*​ must configure a port forwarding for port 7777.

Instructions for port forwarding:
To configure port forwarding, you need to access your router’s interface through the web browser.

1. Run the program “cmd” (Win key + R, then type cmd in the textbox)
2. Once inside the terminal, type ipconfig
3. Write down the IP address of your default gateway. That should be your router’s IP.
4. Also write down your own IP (IPv4 Address)
5. Open the browser and type the IP.
6. Log into your router, and look for a tab or menu called “Applications & Gaming,” “Advanced,” “Port Forwarding/Port Triggering,” “NAT/QoS,” or something similar.
7. Set up a port forwarding for TCP port 7777. Don’t forget to save/activate the port forwarding.

Steps 6 and 7 can vary depending on your router’s brand/interface.
Here’s a more complete guide from PC World: http://www.pcworld.com/article/244314/how_to_forward_ports_on_your_router.html