Custom Menu

I just started using Elgg, and I am creating a plugin right now for a custom main menu.  So for instance, I have a mainmenu.php file located in "mod/myplugin/mainmenu.php".  I tried to use "echo elgg_view( $CONFIG-> wwwroot . "mod/myplugin/mainmenu", $vars);" but it doesn't work!  Can someone please advise on how to include my custom php file as a view?  Thanks!