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
)
);