Thank you @[deleted], I did it.
BTW, do you know how to customize (add/remove/change the hyperlink) menu buttons?
Update: I found the code in class.nav.php but I can not replace the link of these button with other site link, it stay with the root folder of osticket.
Code in line 356:
$navs=array('desc'=>__('My new button title'),'href'=>'I want to change to other site hyperlink here','title'=>'');