The letters that are vowels in English are also vowels in Spanish, but they aren't always pronounced the same. Generally speaking, pronouncing vowels in Spanish is a lot less complicated than pronouncing them in English.
You’re well aware that one vowel in English can have more than one sound. Look, for instance, at fat and fate. Both words have the vowel a, but they’re pronounced much differently from each other. The good news is that in Spanish, you always say the vowels one way, and one way only.
If you want your Spanish to sound like a native’s, you have to concentrate on your vowels. They are
a (ah): atacar (ah-tah-kahr) (attack)
e (eh): entender (ehn-tehn-dehr) (to understand)
i (ee): vivir (bvee-bveer) (to live)
o (oh): rojo (roh-Hoh) (red)
u (oo): cúrcuma (koor-koo-mah) (turmeric)
Spanish sees each of these vowels by itself and makes other sounds by combining the vowels in twos, as in these examples:
abuela (ah-bvooeh-lah) (grandmother)
feo (feh-oh) (ugly)
miércoles (meeehr-koh-lehs) (Wednesday)
The letter y, which can be either a consonant or vowel in English, is only used as a consonant in Spanish.