First, you need to have an array already initialized. If you do not have one, you can use hte function "Initialize Array" to create one. For a 1D array of strings, you can wire an empty array to "Element Data" input and the desired size to the "Dimension Size" input.
Now, you can assign the values to the specified elements using the "Replace Array Subset" vi.
If you attempt to add or modify an element in an uninitialized array, it will not work. Also note that you can't assign values to elements beyond the size of your array.
Regards;
Enrique
www.vartortech.com