Sorting posts by date and category

I have a sidebar on my blog that uses the wp_get_archives() and wp_list_categories() to create a list of links to posts by month and category. I would now like to be able to click on one of the links and show posts in that catetory or month only. I don’t know how to sort them on that page. I think I learned that the archive.php file is the place for this, correct? If so, how can sort my posts on archive.php so they only show the month that was clicked on, or just posts with the category that was clicked on?

Thank you very much for any help on this!!!