Visual C++ :: Letting User Enter A Character On Specific Line And Place?

How can I create in my C++ program so a user can paste a text and then choose a character on specific line and place?. The above thing isn't that important. I just want to place a character on a specific line and place.

I mean something like this:

Enter a character:

You choosed " / "

On which line do want the character?

You choosed "Line 1 and 2"

Where do you want the the to appear on the line? (left or right)

You choose left.

Results:

Line 1. / hello

Line 2. / hello