Just installed an exhaust... need some help.

[beebosaur]

OKay, so I cannot stress enough how new i am to all this car mod stuff. my friend got me an apexi world sport exhaust for my birthday and i had another friend help me install it. after we installed it everything looked and sounded great with one exception. the apexi is much larger than the stock exhaust and sometimes while i'm driving it shakes enough that it starts hitting the bottom of my bumper or something under my car. my friend told me i'd need to get new exhaust hangers but i'm not sure what i'm supposed to be looking for when shopping for exhaust hangers. any help would be awesome. thanks!