TFT screen to change sketches
A TFT screen is just a screen. You can't modify SSIDs and passwords with it, any more than you can by poking your PC monitor (unless perhaps you have a touch-screen*). To modify things you would need:


An input device (eg. a keypad)
A method of displaying what you are entering (this is where the screen would be handy)
A method of storing the new information. You could store things like passwords in EEPROM.
Code to make all that work.


* Some distributors sell touch-screen interfaces designed to go on top of screens - this might conceivably be what you are thinking of. However you still need the touch-screen, and code to make the touch-screen, and the TFT screen, work.