How can i get this girl that goes to the school that i just transfered from?

call her

If you have her number - call her. If not, have a friend that is still at the school talk to her. Have that friend tell her that you'd like to get to know her better, and would it be okay to get her phone #. If she gives your friend the #, great! Call her! If not, thank your lucky stars that you're at another school and will never have to see her again, and find someone just as cool at your new school. Just be sure when you have a friend help you, that s/he is a good friend who will ask the question simply and honestly and won't throw in a bunch of BS trying to be cute and funny.