How to enable particular category?

On the main page of the blog, each time I made a post, it always show the post. But I just want to show the post that I have made in a specific category.

Suppose I have created two category called: Cat 1 and Cat 2.
Then I made two post, one on Cat 1 and the other on Cat 2. If I go to my main blog page, I will see that there’s two post. But I only want to see the post that I have made in the Cat 1. What should I have to do?

Thanks!