toki pona has 14 letters in its alphabet:
a e i k j l m n o p s t u w
the vowels are similar to spanish.
a [ä] - like a in father
e [e̞] - like e in let or ten
i [i] - like ee in bee
o [o̞] - like o in cone
u [u] - like oo in soon
(note that the comparisons to english words are approximations and may not be accurate depending on your accent, i recommend going by the IPA symbols inside the square brackets for a more accurate idea of the correct pronunciations)
most of the consonants are just like english, except j. j is always like y in yellow
don't be stressed, you don't have to pronounce the letters exactly as i say, you can pronounce things slightly differently if it feels natural - for example, you could soften your p, t, and k sounds into b, d, and g sounds!
oh and also, you always have to stress the first syllable of every word.