Here's a breakdown:
* STEE: The "ee" sound is similar to the "ee" in "see" or "tree."
* vən: The "v" is pronounced like the "v" in "very," and the "ən" sounds like the "un" in "sun."
Some people might pronounce it STEE-fən, where the "f" is emphasized slightly more. However, the STEE-vən pronunciation is more widespread.