How to show different categories in different pages?

Change the cat to the category number you want. For example:

 "cat" => 2, 

Or if you know the category name you could also use:

"category" =>"category_name", 

You should add any of the above two lines in your wp_query arguments like the one in below which is empty:

$wp_query = new WP_Query( array( 
                                                    "cat" => "", 
                                                    "posts_per_page" => "", 
                                                    "post_type" => "post",
                                                    "paged" => get_query_var('paged') ? get_query_var('paged') : 1
                                                    )                                               
                                            );