Where are you from? What nationality are you? What is your nationality? Keep in mind that it can be complicated and it's often not clear what it is that people are asking you, what it is that they want to know. Often they are asking about your citizenship when they mean your cultural and religious ancestry, or vice versa. For example, I am Serbian by nationality (inheriting my father's origins), I was born in Croatia (and my mother is Croatian) and I've lived in the US most of my life. I live in Slovenia now and I hold two citizenships, and could probably get a third one if I wanted to. I consider myself a Serbian American but I can't reply to your question with a simple one word answer.

Im from Venezuela!

I don't understand the question "how to use?" though I would answer the rest of your questions, well I'm from Mexico, and I'm Mexican.