How do I mimic the "Tab" function on a desktop keyboard? I need to enter text on a mobile phone.

to tab between text fields, you use the joystick/navigation keys. Provided you
haven't hidden the hilight, a bright yellow rectangle will surround the
currently selected text field or button. when you get to the desired spot,
press enter (press in on the joystick), and it will bring up the OS style text
input window.