Hm... I don't think you need to use array at all. There are special system functions that seem to do the job you'd want.
Some functions you should know:
-Left(string,N)
-Right(string,N)
I'll explain these later.
So what I've read you want something like "here's the text, now copy it".
Ok. First the variables:
Paragraph = "Bla Bla Bla Bla"
TheLetter = ""
Now this is the logic. I don't know how you'll fit it into your game but you'll manage. Using Left() you can find the very first letter of any string chosen:
TheLetter = Left(Paragraph,1)
This function Left() will cut down the string Paragraph to the number (ie, in this case the very first letter of Paragraph). Once we cut down Paragraph it will be something like "B" and will be the variable TheLetter.
Ok so you'll need to detect the key pressed which will equal TheLetter. This is a trick I do not know, at least for now.
Once the key pressed equals TheLetter the game should remove that letter by using Right() which works the other way than Left().
Paragraph = Right(Paragraph,Len(Paragraph)-1)
This will remove the first letter of Paragraph and will leave it with "la Bla Bla Bla".
Then you can make it cycle again.