Add the following to your funcitons.php file
function skp_custom_user_create_fields($user){
if (!is_super_admin( $user_id )) {
?>
<table class="form-table">
<tr>
<th scope="row"><?php _e('Skip Confirmation Email') ?></th>
<td><input type = "checkbox" name = "noconfirmation" value = "1" <?php checked( $_POST['noconfirmation'], 1 ); ?> /> Add the user without sending an email that requires their confirmation.</td>
</tr>
</table>
<?php
}
}
add_action("user_new_form", "skp_custom_user_create_fields");
function skp_auto_activate_users($user, $user_email, $key, $meta){
if(!current_user_can('manage_options'))
return false;
if (!empty($_POST['noconfirmation']) && $_POST['noconfirmation'] == 1) {
wpmu_activate_signup($key);
return false;
}
}
add_filter('wpmu_signup_user_notification', 'skp_auto_activate_users', 10, 4);
That would do the job.