error loading an array of strings
So, you are confusing the object String of Arduino with a string of C (char array), to solve your problem, I've changed your code in two parts:

String titles[] = {"entry one", "entry two", "entry three", "entry four", "entry five"};

void setup(){
  Serial.begin(9600);
  Serial.println("Storing numbers in an array");
}

void loop(){
  for (int x = 0; x &lt; 5; x++){
    if (Serial.available() &gt; 0){
      Serial.println("Enter a word... ");
      titles[x] = Serial.readString();
      Serial.println(" ");
      Serial.println(titles[x]);
    }
  }
}


So, in order to use Seria.readString(), you have to use String objects to receive the data from Serial port:

String titles[]


Instead of:

char* titles[]


The second change is related to Serial.println(chartitles[x]), I didn't understand what you mean with this code, so I changed in order to print the String that was read.