* SHIH-len: This is the most common pronunciation, treating "Sh" as the English "sh" sound and "ilen" as a separate syllable. This pronunciation is most likely if "Shilen" is a name of a person or place.
* SHY-len: This pronunciation stresses the first syllable and uses the "sh" sound with a softer "y" sound following it. This pronunciation is more likely if "Shilen" is a word from a fictional language or an invented term.
Ultimately, the pronunciation depends on the context. If you have more information about where you encountered "Shilen," it might help narrow down the pronunciation.