You need to remove the hub.
I suggest you get a service manual. In a nut shell:
1) remove freewheel hub cover ... remove snap ring, cone washers hold on the body.
2) You will need a large socket, 54mm comes to mind. First nut on the spindle will have a tabbed washer underneath. Pound back the one ear holding on the nut. Remove first nut.
3) remove tabbed washer.
4) remove next nut.
5) give the hub a tug. There will be a large washer next, then the outer wheel bearing. They will probably fall out so get ready to catch them.
6) Hub with rotor will come off spindle.
Removing the rotor from the hub.
1) Remove bolts on back side of rotor.
2) My method for removing studs is get a brass hammer. Set brass hammer on stud. Smack brass hammer with 2-3lb BFH until stud fall out the bottom. Smack hard. Repeat.
Installation is the reverse, but again read the service manual for torque specs to set the bearing preload. As far as things to do while there ... replace wheel bearing, repack with grease. Replace inner hub seal. If your inner axle seals are leaking be prepared to take the knuckle a part while you are there and replace those. Big job, but it needs to get done.