When applying for the Vietnam e-visa, you will be asked to enter your personal information. This includes your complete name, date of birth, nationality, and some relevant details from your passport. So before you start with your online application, it is best to have your passport beside you.
Do not be in such a hurry to submit the visa. Take time to review the information you entered. Otherwise, your e-visa will be delayed. Also, you could be prevented from entering Hue if the details in your passport do not correspond with that of your visa.