You can use:

alert("Hello World!")

Or if you want a dialog box that let's you make a choice, you can use;

let check := dialog("Create Record", "New record will be created. Please confirm.", ["Continue", "Cancel"]);
if check = "Cancel" then delete this else void

essentially you are just using the dialog() function to obtain a choice from the user, and then saving that choice as variable "check" and then taking a certain action based on what value was saved to the variable "check"