I assume you mean YHWH. That is a transliteration of the Hebrew name of their god. I can't post the Hebrew alphabet with this browser, but the letters are yod he waw he, and of course they run from right to left. (In Yiddish and modern Hebrew it's pronounced vav, not waw, and customarily transliterated as V except in this one word.)
Hebrew is normally written without vowels, which are diacritical marks under the letters, since vowels are not phonemic in the Semitic languages. So it's natural for this name not to be written with its vowels. It could be argued that no one really knows the correct pronunciation! This is the name that we transcribe into Latin as Jehovah, with J and V in classical Latin equating to Y and W sounds. So you would not be too far wrong to pronounce it as Jehovah, either the customary English pronunciation or scrupulous Latin phonetics, ye-ho-wa.
The Hebrews had a superstition about not pronouncing their god's name, at least not correctly. So it's not clear how it's supposed to be pronounced! The most common way I've seen it written out by people who aren't religious Jews is Yahweh. I don't know if that's some modern convention or if there's actual evidence of it once being pronounced that way by the ancient Israelites. In any case you'll be in good company if you say it that way too.
Or you can just insert your own vowels. That way you'll be following the religious custom of making something up in order to not pronounce the god's name correctly. You could say Yuhaweh or Yihwoh. Of course since nobody knows what's correct, you could accidentally stumble onto the right one. I don't know what would happen to you. Pillar of salt? Plague of locusts? Bolt of lighting? Exile in Egypt? Eternity in the Bog of Eternal Stench?
