Your code should probably look like "char str[]" or "char x[]"
Inserting a null to "end" the string...
First, use a loop to search for a space. x[n] == ' ';
Code:
char x[] = DougDbug;
x[4] = '/0'; // Replace the second 'D' with '\0' So that "Doug" will print-out.
Inserting hyphens...
First, you have to shift-right all the characters right of the hyphen.
So, again in a loop (starting at the end and working backwards).
Code:
ssn[4] = ssn[3]; // Move the character in position 3, to position 4
ssn[3] = '-' ; // Overwrite position 3 (4th character) with a hyphen.
[EDIT]
BTW - What you are working with is a "character array" or "c-style string". An example of an "array of strings" would be a an array of sentances, which the computer would see as a two-dimensional array. Or, "an array of character-arrays".