How to get in shape for girls outdoor track??!?

URGENT! I might be joining next week. Im not a complete noob now, I ran track for about three years [age 8-11] but im 14. I'm not COMPLETELY out of shape, I haven't gained like a huge ammount of weight or anything [117] andd I REALLY need to get in shape quickly, or at least be able to run a 1500 [mile, basically] without ping out. I could go joggin and all, but i have little time [high schooler]