Read James Brooks‘ answer to How do you pronounce “primer”? on Quora

I pronounce it like this (using the International Phonetic Alphabet): /ˈpraɪmə/. There are two syllables with the stress on the first one, resulting in something like PRI-mah.

If you want to learn more about the International Phonetic Alphabet, you can find a guide here: International Phonetic Alphabet and Phonemic Alphabets