Gather tools and materials: toilet, wax ring (or flange gasket), closet bolts, shims, adjustable wrench, screwdriver, level, putty knife, caulk, supply line (if needed), bucket/rags
Turn off water at the shutoff valve
Flush to empty the tank and bowl
Disconnect the water supply line from the toilet tank
Remove the tank-to-bowl bolts (if applicable) and separate the tank from the bowl
Remove the toilet by unbolting the closet bolts and lifting straight up
Scrape away old wax and clean the flange surface
Inspect the flange for damage; replace flange if cracked, loose, or below floor height
Confirm the flange height is correct; if too low, add a flange extender or replace the flange
Position closet bolts in the flange slots (replace if necessary)
Place the wax ring on the flange (centered) or install the flange gasket per its instructions
Set the bowl onto the flange, aligning bolt holes with closet bolts
Press down firmly and evenly to compress the wax ring
Check bowl level with a level; adjust with shims if needed
Install washers and nuts on the closet bolts; tighten until snug
Do not overtighten to avoid cracking the toilet
Trim excess closet bolt length if needed
Reinstall the tank onto the bowl and tighten tank-to-bowl bolts
Reconnect the water supply line to the tank
Turn on the water supply
Check for leaks at the supply connection and around the base
Flush and inspect again
Apply a bead of caulk around the base where it meets the floor
Wipe away any excess caulk and clean up the work area