Ivy League Supplemental Essay?

Hello, I am trying to write a convincing supplemental essay for a couple of Ivy League schools and I have already written what I called a very good essay for the Common App essay already. I am having trouble figure out what to write about. My Standardized test scores are not good enough compared to the average of those Ivy League schools (maybe because I am weak in English, I came to this country about 3 years ago with another language), but I have a strong academical record (including high school grade). Do you have any advice on how to wow the college admission officers with my supplemental essays. And what essay topic (or focus) do you think will be perfect for this situation, the supplemental question is limitless. I need help please. Time is winding. Thanks

We don’t know anything about your life experiences, but try to think of what you want to say about yourself first, and then work backwards to see what experience illustrates that best.

Thanks for the advice, I think it will be great if I can write about the education I had in my native country. Do you have a say?