If the boot pulled loose from the inner joint you need to investigate why this happened. The band that holds the boot in place has most likely failed. It can be replaced. If the boot is in good condition then get a new band. The ends of the band can be seperated, wrapped around the boot, and put back together.
Then there is a special tool for "crimping" the band to pull it tight around the boot. (If there is an indication of a loss of grease in the joint the axel should be removed so that the joint can be cleaned and repacked with grease.)
This can be done with the axel in place, but the room for doing this is minimal at best. If the boot is split or cracked it has to be replaced. The axel has to be removed to do this. Then the joint has to be removed so that the boot can be removed after the small clampping band is removed. A boot kit will have the new boot, two new bands, a new "cir-clip, and C/V joint grease.
The inner joint is a "yoke" type joint with three rollers mounted on needle bearings. Do not take these apart and risk losing one of the needle bearings (MANY). Clean out the joint and repack it with grease (C/V joint grease). rangerj