If you want to play with others on the same local network (LAN), google how to find your local IP for your operating system.
If you want to play with people NOT in your network, you have to either
- play over a virtual private network using e.g. Hamachi (that CAN be a bit of a hassle, though, as those programs usually need to be installed for all players and sometimes malfunction, too)
- or you need to forward the ports Minecraft uses in your router (which can also be a bit of a hassle due to various firewalls). There’s lots of info on that in the Google as well.
The IP for people not in your local network is different from your local IP,
- for Hamachi it’s a dedicated Hamachi IP that would be displayed in the program
- in case you port-forward, you have to google your global IP, there are websites that display it to you.
Note that you shouldn’t give your global IP to people you don’t trust, i.e. don’t post it somewhere public.