What do you mean exactly? If you want to declare strings, you just append a dollar sign to the variable identifier.
E.g.: ST$ is a string.
If you want to print it, simply use PRINT <String Variable>.
E.g.: PRINT ST$
Well, that's really simple to implement. You just have to remember that a string is really just a string of individual characters. You could have a FOR loop that iterates over the string and prints each character.
E.g.:
FOR I=0 TO LEN(ST$)-1
PRINT ST$[I];
WAIT 20
NEXT
Ok, here's what I want to know. How do I make it so the text types one letter at a time, like I do
PRINT "Hello World"
And if you run it types out the phrase one letter at a time so it looks like its typing it out for you.