"Your garage is pretty, Samia."
Translation:كَراجِك جَميل يا سامْية.
Well, first of all:
An accent above the letter is called (fatHa): and this is short vowel (a).
And accent under the letter is called (Kasrah): and this is short vowel (i).
And a little Waw و above the letter is called (Dhammah): and this is a short vowel (u).
In case your question is regarding the sound, I think the above brief would do. In case your question is about knowing the proper placement in general, then this is related to grammar in Arabic.
The audio you hear here is wrong in fact, as the word should be (Karájuki) كَراجُكِ (and it's not even a proper Arabic word, rather dialectical) - because the word is in nominative case (nothing is affecting the word) and the natural ending for such word should be (-u), which is then followed by the possessive suffix (-ki) for "your/f".
The change in the ending vowel in Arabic is linguistically called "Declination" and many other languages practice such thing, like Russian, when words change its position in the sentence from nominative to accusative (a verb acts on it) or genitive (OF-relationship between 2 words)... etc.
Hope this answers your question.