You have to replace wax ring- do it soon before filthy water starts
rotting out the floor. You know how? Turn off water supply, flush
toilet, remove residual water from tank with small container/ rag.
Disconnect supply line. If this is one- piece, you are ready remove
bolts and lift- if two- piece you must first remove tank- you will
need new tank bolts/ gasket(as well as wax ring, closet bolts, also
check condition of supply line, replace if necessary). After you lift
it, check condition of flange, replace if necessary, clean bottom of
toilet and floor very well,final clean with rubbing alcohol, warm wax
ring a little and apply to bottom of toilet- my bro, who does
bathrooms for a living 20 yrs, insists this is better that putting it
on floor first, where you may damage it when lowering toilet- he also
says use 2 rings if you like to be sure of good seal. Get toilet as
close to perfect level as possible, snug bolts, replace tank, supply
line, caulk around toilet.