If you're just using the default 2006scape servers, or any offspring of that, you could either make a command, or do it the default way in the Player.java class.
In Player.java, find and replace your getStaffRights() method with this and put your name in the String parameter shown.
Code:public int getStaffRights() { if (getUsername().equalsIgnoreCase("your name")) { return 2; //Admin } return staffRights; }