You have to jack up car, block it up securely, remove the front tire, remove the tie rod, lower balljoint, the nut that holds the Axel to hub, pull hub/rotor out of the way, slip out the Axel and install new joint or rebuilt Axel. A rebuilt Axel is best to install, it has new joints and is about as cheap. Reverse to install. This is not a job for the novice mechanic though.