It depends on if you have port forwarded. (Important keywords in bold.) Port forwarding is the process of opening ports on your router to allow connections from other computers. Usually, you can just google "Port forward (Your router name)" and find out how. Make sure its port forwarding, not port triggering or DMZ (unless you want less security.) Next, you will need your ipv4. You can go to ipchicken for this. Next, send your friend your ip and port that you opened for NOVETUS. If you are joining your friend, make sure they have port forwarded. If they have not, upnp may work. If not, then teach them the steps on how to port forward using this guide, and your should be able to join them! Also, make sure your NOVETUS is up to date. If it is not, then update, or make sure your friend updates to your current version!
That is all, I am heree.