əˈsoʊ.si.eɪt
Here's a breakdown of the sounds:
* ə - like the "a" in "about"
* ˈsoʊ - like the "so" in "so"
* si - like the "see" in "see"
* eɪt - like the "ate" in "ate"
Example: The stress is on the second syllable, "so".
You can listen to the pronunciation on a dictionary website like Merriam-Webster or Oxford Dictionaries.