You will need to strip the old wax off.For that you need a floor stripper.If you are not familiar with strippers be SUPER careful.
Trouble with them is 1.you think you've rinsed really well, but the smallest amount of stripper will lift the wax after it's dried!!
To save yourself the trouble of this happening use ammonia.I know, I know it stinks! and bad, but it's cheap and you won't have to worry
about not getting it off the floor as much as those fancy pricey stripper concoctions.
So you are going to have to strip, rinse, and this is critical THE FLOOR MUST BE BONE DRY and not just on the surface but down in the tiny cracks and around the edges of the tile or again the wax will not be wax for long as it will turn to powder.
So the floor is stripped (it looks really dull, no shine) it's bone dry! YES?.Now you can apply the wax using a small wax applicator.
You can get wax at a janitorial supply house as well as a small wax applicator.