Step 1 - Find your Router IP address.
Find your router ip by typing in ipconfig into cmd. Look for your default gateway ip.
Reference photo[photos.google.com]

Step 2 - Set your static ip address.
Set your static ip address by going into control panel -> network settings (view network status and tasks) -> change adaptor settings -> ethernet/wifi -> properties -> internet protocol version 4 -> properties -> use following ip address - (your current router ip address with the last number as 251) xxx.xxx.xx.251, subnet mask 255.255.255.0, default gateway same as it says in ipconfig.
Reference photo 1[photos.google.com], Reference photo 2 [photos.google.com], Reference photo 3 [photos.google.com]

Step 3 - Port Forwarding
Type in your default gateway ip address into your browser to bring up your router configuration menu. The port forwarding option will be different based on your router model, in this case mine is under NAT - Virtual Servers.
Create a new a new service, write the server IP as your new static IP that you just made, enable LAN feedback if that is an option, and set the ports start and end - 3075, 27015, 27215 TCP and UDP.
Reference photo[photos.google.com]

Step 4 - Check if server is online and working.
Boot up LP:EC and create a lobby. Go back to steam, click on view -> servers -> internet -> Search by game - LP:EC. You should be able to see your lobby in this window.
Reference photo[photos.google.com]

All done, this should be achievable in 15 minutes!

If this was helpful, please rate the guide 5 stars :)
Dont hesitate to ask any questions or if you need assistance.

Happy hunting, Snow Pirates!