You get stars by your name by having a certain ratio of wins to losses. For example, having a 5:1 ratio might get you 1 star, while a 10:1 ratio could get you 2 stars. As for capturing a flag, I think you point at the flag and press A.
I have tried to point at the flag and press A but it does not work. I think you might have to get a grunt etc to stand really close then point and press A but cant get it to work properly. Other people do it against me to good affect so it is getting frustrating!!!! I would have won so many more battles if I could do this!!