First, what you need is a couple of the world level functions (see attached - there are a few of them
).
"Ask user for ---" will get your input and "--- as a string" will convert it to string format if it wasn't one already.
Two options to display the string on screen while the world is running are the "say …" command and using the string as the text in a 3D text object. (Anyone know any others
?) Also, the "Print" command (drag up from the bottom) will print almost any type of variable in a small text box below the screen.