I should have posted here sooner, since I figured it out within 15 minutes of asking how to do it
If anyone else wants to know here's how:
Create your php file in the admin folder -> xcart_dir/admin/file_name.php
PHP Code:
require "./auth.php";
require $xcart_dir."/include/security.php";
$location[] = array("New File Menu", "");//bread crumb menu
$smarty->assign("main", "file_name");//skin/single/home.tpl
# Assign the current location line
$smarty->assign("location", $location);
@include $xcart_dir."/modules/gold_display.php";
func_display("admin/home.tpl",$smarty);
Then make the template file under skin/admin/main/file_name.tpl
Code:
{include file="page_title.tpl" title="Page Title"}
//additional smarty code...
Finally edit skin/single/home.tpl and add an elseif statement like so
Code:
{elseif $main eq "file_name"}
{include file="admin/main/file_name.tpl"}
Of course add the link in the admin menus which I haven't done yet