Restrict home page posts to certain categories

functions.php

function my_home_category( $query ) {
 if ( $query->is_home() && $query->is_main_query() ) {
 $query->set( 'cat', '11');
 }
}
add_action( 'pre_get_posts', 'my_home_category' );

//If you would like to include more than one category, then just add another ID by inserting a comma and the ID number. For example, this is will display category 11 and category 14.
//$query->set( 'cat', ’11, 14’ );