It's going to depend on what environment your application is to run in: a CLR app could use one String class which has Substring functions, while a native app might have to use a different string class which supports substr instead.
But basically the operation will be along the lines of:
newstring = substring(original, 0, 1) + " " + substring(original, 1, lengthOfTheOriginalString - 1)
Check your classes for the exact functions and parameters to use.
And you do realise that in essence, any string
is a character array?