It's pronounced roughly like "feht" with a short "e" sound at the end.
Here are some examples of how it's used:
* "On va aller à une fête ce soir." (We're going to a party tonight.)
* "Y'a une fête chez les Dubois." (There's a party at the Dubois's house.)
* "C'est la fête!" (It's a party!)