Trouble using Brackets

The code below was copied from another forum. I pasted it into a new page in Brackets but could not see any functionality. I don’t understand how this thing works, apparently. There’s no “run” command, for instance, so how does Brackets know when I’m ready to test my code?

debugger;
if (positionInArray <= 0) {
return array[0];
} else {
return sum (array, positionInArray - 1) + array[positionInArray];
}
}

console.log(sum([2, 3, 9], 1));```

brackets doesn’t run code that easily
you need to use the Live Preview feature

This video seems to be about that, it may be useful for you