kwiˈɛs(ə)ns
Here's a breakdown:
* kwi - sounds like the "qui" in "quick"
* ɛs - sounds like the "ess" in "dress"
* (ə)ns - the "ə" is a schwa sound, like the "a" in "about", and the "ns" sounds like the "ns" in "sense".
So, it sounds like "kwi-ess-ence".