How to get authors who have added the post in the specific custom post type

When you say “who have added the post”, are you meaning all users who have written at least 1 post of the event post type? If so, you can get all the authors of all events like so:

$event_posts = get_posts([
    'post_type' => 'event', // Or whatever your event post type is
    'numberposts' => -1,
]);

// Get all the author (user) IDs of all events
$event_author_ids = wp_list_pluck( $event_posts, 'post_author' );

// Now get all the user objects
$users = get_users([
    'include' => $event_author_ids,
]);

Alternatively, if you are meaning the author of the current event post, there can only ever be one author per-post, and you can just use the author template tags whilst in the loop.

echo get_the_author_link();
// Get author <a /> HTML

echo get_the_author_meta( $prop );
// Get author property e.g. display_name, user_email, first_name etc.