How do you get a medal in Star Wars battlefront 2

It depends on what for medal you want I mean that one what called something with trader you have to kill your own man.

It differs from platform to platform. Some by sniping so many people in the head; killing so many people with certain weapons in one life; get so many points in one life. I recommend that you go to where you can see how many medals you have and look: it usually tells you how to get them. If that doesn't help, go to (the website in the related links) find the game on the platform you have, select guides/walk throughs and it should tell you.