@HailuMu - I believe that once you receive the invitation, you are qualified. Only the students who made the cut-off for their region (with the South requiring an SI of 204 this year) are invited. You still have to fill in a form and have your guidance counselor confirm your information.
As there is no scholarship money attached to the “title,” it is not as work-intensive as National Merit. However, there are special scholarships for Hispanics available and some universities treat “National Hispanic Scholars” as well as “National Merit Scholar Finalists.”