You’ll install the boot between the steering knuckle before you slide the ’shaft through. The company provides a special seating tool that allows you to properly set the boot on the bell. Be sure to grease the end of the ’shafts splines and make sure it’s lined up properly. Never force the ’shaft in. The JK front axle seals are not the best, and it doesn’t take much to rip one and end up with a gear oil leak.