C :: Creating Variable Length Arrays

How do you prompt the user to enter the number of elements for the array and use that information to creatr a variable length array? And then how do you prompt the user to enter in a number for each element of the array and scan in the appropriate numbers? the numbers are double precision floating point.

for example,
Enter the numbe of elements in the array: 3
Enter element 0: 3
Enter element 1: -1
Enter element 2: 4

I know it starts with

int main() {
double N;
int a[size];

printf("Enter the number of elements in the array:" );
scanf("%f", &size);

//I'm pretty sure this is wrong