How to capture ethernet traffic?

edit

I tried to analize what was written there but couldn't understand how to setup the program. By default the program had Promiscuous mode turned on, I read somewhere that router should have port mirroring but I couldn't find it on my router. Is there any way to trace other computer traffic ?

I converted your answer to a comment, as it is more a comment. You should read the packet capture playbooks: https://blog.packet-foo.com/2016/10/t... As I think they explain your questions. And a mirror port does not every sitch have.