Use it when referring to every aspect included in something, like a full deal or offer. The new job provided the whole ball of wax - high salary, health benefits, and a company car.
Pro Tip 2/3
Not Literal
It's a metaphorical phrase, not about an actual ball of wax, but about having all one could need. The holiday package was the whole ball of wax, with flights, hotel, and meals included.
Pro Tip 3/3
Informal Speech
It is casual language, more suitable for everyday conversations than for formal writing. This toolbox has the whole ball of wax for your home repair needs.