not sure where to start, feel confused

Alright. So basically a do..while loop is a while loop, that always runs once.

So was we know a while loop, will always run until it's loop condition is satisfied, however, it may not always run if the condition is already met. Sometimes, we want the body of the loop to always run at least one, a do...while loop allows us to do this.

How? Well here's the syntax

do {
  // whatever you needed to do inside the loop
} while(condition is not met);

In our specific case we need to make sure that the prompt is always run at least once so let's re-write and re-arrange the code a little by converting this:

// Display the prompt dialogue while the value assigned to `secret` is not equal to "sesame"
let secret = prompt("What is the secret password?");

// This should run after the loop is done executing
alert("You know the secret password. Welcome!");

to this:

// Display the prompt dialogue while the value assigned to `secret` is not equal to "sesame"
let secret = '';
do {
  secret = prompt("What is the secret password?");
} while(secret !== 'sesame');

// This should run after the loop is done executing
alert("You know the secret password. Welcome!");

This is how we would accomplish the task. However, instead of just copy pasting this code, I recommend you go back and watch previous videos again to get a better grasp of the subject before moving on. That way you properly learn the content!