How do I display posts with specific value in a custom field into my loop?

Use the meta_query argument of WP_Query. For example, if your custom field name is “year” and you want to get the post with year=2013:

<?php
    $loop = new WP_Query( array( 'post_type'      => 'Sport',
                                 'posts_per_page' => 3,
                                 'meta_query'     => array( 'meta_key'   => 'year_comm',
                                                            'meta_value' => '2013',
                                                            //Assuming you are using numeric value
                                                            //if not, delete the next line
                                                            'type'       => 'NUMERIC'
    ) ) );
?>

Or use the custom field parameters:

<?php
    $loop = new WP_Query( array( 'post_type'      => 'Sport',
                                 'posts_per_page' => 3,
                                 'meta_key'       => 'year_comm'
                                 //Assuming you are using numeric value
                                 //if not, use meta_value
                                 'meta_value_num' => '2013'
    ) );
?>