Here is my suggestion:
1. Google with words like "motivation letter" or "personal statement" (plz use english), then you can find some samples writtten by foreigners. Samples in relation with your major could be better!
2. You may organize your statement with a clue like: YOUR GOAL----WHAT THE PROGRAM CAN OFFER TOWARDS THE REALIZATION OF YOUR GOAL.
3/ Think as you are one of the admission board, ok? You must give them the info they want in the paper.