She is my sister. Sue is twelve years old and I am sixteen.
We aren't adults. We are students. We are Canadians. We are Americans.
We are from Chicago. Chicago is in the United States.
Rule for knowing when to use is : Use when talking about a single thing
Rule for knowing when to use am: Use when talking about yourself
Rule for knowing when to use are: Use when talking about multiple things.
Hope my little explanation at the end made sense and helped a bit. Let me know if you need more help!