Disable delivery method tab or step4 from checkout page in opencart

open file checkout.tpl

catalog\view\theme\default\template\checkout\checkout.tpl

step 1) : 
 find
$('#shipping-method .checkout-content').slideDown('slow');
 Replace with
 $('#shipping-method #button-shipping-method').click();

 Step 2):
 And find  <div id="shipping-method">
 And Replace with <div id="shipping-method" style='display: none'>

 Thats all . Enjoy it.