fəˈnɒmɪnə
Here's a breakdown of the pronunciation:
* fə: Like the "f" in "fun"
* ˈnɒ: Like the "on" in "on" but with a short "o" sound
* mɪ: Like the "mi" in "mile"
* nə: Like the "na" in "name"
Note: The word "Phaenomena" is a less common spelling of the word "phenomena."