Manipulate textfield position

You'll need to know the x,y position of course.  You could ask the user with a dialog box - or it could be passed on the command-line, from a preference file - or any way that seems appropriate to your application.

You can set the window position with
NSPoint p ;
p.x = x ; p.y = y ;
[window setFrameTopLefPoint:p];

Of course you have to know window and you may know this via the awakeFromNib, windowDidLoad, a delegate or some other way.  Without knowing more about your code, I can't say which of many methods should be used.