adding posts to a category wordpress : anybody!

My question is about **posts and category**. What is **right php template** for adding posts to a category so that **new posts would be displayed in order for a specific category?**

So , I have single.php, I have category.php. Do I need archive.php as a must or no? 
For example, I want to put a category in my menu, then click to that category to view posts but even if I link new posts to that category, none are displayed. Indeed, I can view my posts individually but not if I go to a category page.
What should I do to figure out it right?

Anybody knows? 