I have seven badges but I'm stuck on getting number eight could someone..

First of all, Azurill doesn't evolve at a level. He evolves when you level him up while he likes you a lot.

Second, visit Lake Acuity. Then, go to Veilstone and talk to the grunt outside the Galactic HQ. Pick up the key he drops, and with this, access the Warehouse, and maneuver through there to obtain the Galactic Key in the end. With this key, access the HQ and maneuver through that to battle Cyrus (after the battle, he gives you the Master Ball), and then if you continue a little bit, you'll battle Saturn. Free the 3 pixies, and then go to the top of Mt. Coronet through the entrance near Oreburgh City. Just keep in mind that you need to go as far north as possible, and when that doesn't work, go as far west as possible. You'll eventually reach the top (Sky Pillar) and notice you have quite a few battles in front of you. Battle the two grunts, battle the two commanders with your rival, and then beat Cyrus. When you beat him, heal up and save your game. Battle (and try to catch) Dialga, and when the battle is over, you can now access Route 222 and go on to Sunnyshore City to obtain the eighth badge.