using an index number, append that index (a character) to char array

I'm attempting to do something like this.

class testClass {        
  public:              
    void testFunction(char charArray[])
    {
    char output[].append(charArray.at(1));
    char output[].append(charArray.at(7));
    char output[].append(charArray.at(3));
    cout << output;
    }


int main() {
  testClass testObject;
  testObject.testFunction("Flowers"); 
  return 0;
}
   


}

What it's meant to do is:

• get the Letters 'F', 'S' and 'O' from the char array from an index number
• append that char to the output chararray

It's been frustrating since I've went from strings, to *chars, and char arrays.

Not really sure what the simpliest easiest solution is. Yes, I want to retain 1 char at a time from that string. It was just meant to be a fun project but it's way more complicated than I thought it'd be

---

expected output:

• FSO