You want to use strlen() instead for the length of a string and you want to print characters (%c):
int i = 0;
for (i = 0;i < strlen(myString);i++){ // to get a string's length, use strlen
printf("%c\n", myString[i]); // to print a single character, use %c
}
Why use strlen() over sizeof()? Well, in this particular instance, it won't make a difference; however strlen() is for giving you the number of printable characters in a string whereas sizeof will return the size of your array (printable characters + 1 for null terminator).
int len1 = sizeof(myString); // 15
int len2 = strlen(myString); // 14
A) you won't see that printed so it doesn’t help
B) if you get in the habit of using sizeof on strings you might use it within a function you pass your array to (in which case the array will decay to a pointer) and then you'll get back the size of a char * not the number of characters at all. Same applies within the same function if you had done char *myString = "Amazing String";
sizeoflike that.