Step 1: Function Declaration

The first step in solving this function is creating a function declaration. In JavaScript, a function is declared using the keyword function followed by the name of the function, in this case, multiplyTwoNumbers.

function multiplyTwoNumbers() {

}

Step 2: Adding Parameters

The next step is to add parameters to the function. These will be the two numbers that we are going to multiply. In JavaScript, parameters are added inside the parentheses right after the function name. Let's call our parameters num1 and num2.

function multiplyTwoNumbers(num1, num2) {

}

Step 3: The Function Body

In the function body, we will define the logic of our function, which is to multiply the two numbers. JavaScript uses the * operator for multiplication. We will store the result of the multiplication in a variable named result.

function multiplyTwoNumbers(num1, num2) {
    var result = num1 * num2;
}

Step 4: Returning the Result

In JavaScript, a function can return a value using the return keyword. This value can then be used elsewhere in your program. Since we want our function to return the result of the multiplication, we will add a return statement at the end of our function.

function multiplyTwoNumbers(num1, num2) {
    var result = num1 * num2;
    return result;
}

Step 5: Function Call

Now that our function is complete, we can call it with two numbers as arguments. The function will then multiply these numbers and return the result.

multiplyTwoNumbers(5, 3);

Conclusion

We have just created a function in JavaScript that multiplies two numbers. This is the final code:

function multiplyTwoNumbers(num1, num2) {
    var result = num1 * num2;
    return result;
}

multiplyTwoNumbers(5, 3);

In this code, multiplyTwoNumbers(5, 3) will return 15, because 5 * 3 = 15. The returned value can be stored in a variable or used in any other valid way as per the programmer's needs.