Get value from option tree wordpress

option tree with field id “facebook_url” then:

<?php if ( function_exists( ‘ot_get_option’ ) && $test_input = ot_get_option( ‘facebook_url’ ) ) { ?>
<a href=”<?php echo $test_input;?>” target=”_blank” ><img  class=”push” src=”<?php bloginfo(‘template_directory’)?>/images/facebook.png” alt=”facebook” />  </a>
<?php } ?>