Lets look at the vowel marks - the English pronounciation is given as an example in a word, eg the short i is as in the English word Miss

Lets take the letters M and N and add these vowel marks after the M . Note that although the AE and AAE sounds follow after the letter M , they are put before it .Note also that for the O and Au sounds to mark M there are two components of the vowel mark -one which is put before the letter and the other after. These are marked below.

Revise the vowel marks again

And how they modify M

It is important to go over the previous figures again and again until they are imprinted on your mind. Reading the vowel marks correctly is half the battle.
Sameer's comments on the vowels

The  vowels are different from Hindi to Bangla:


aw    (NOT the same sound as in Hindi, it is the sound in "hot" or "lot")
aa    (similar to Hindi)
i       (similar to Hindi)
ee    (similar to Hindi)
u      (similar to Hindi)
oo    (similar to Hindi)
ri      (similar to Hindi)
e      (similar to Hindi)
oi    (NOT the same as in Hindi, it is the sound in "loin" or "join")
o     (similar to Hindi)
ou   (NOT the same as in Hindi, no similar letter, it's just an "o" that
becomes a "u"      making an "ou" sound)