Start by dividing the word up into : "Iss-a-char"
Then, :
-pronounce 'Iss' as in "Miss' but without the M as in '[M]iss'
- 'a' as in the 'u' in 'but'
-'char' as if it is spelt 'car' but pronounce it with a gutteral 'c' as in 'kar'
Last but not least, put the stress on the first syllable ie on 'Iss'