You will need to be at least 13 years old to create a Facebook account. Facebook accounts are free, but you can purchase things for your Facebook account. You can only create one Facebook account per email address. On the Facebook homepage, enter in your first name, last name, email address, password, birthday, and gender. You must use your real name for your account. Nicknames are allowed as long as they are a variation on your real name (Jim instead of James, for example). If all of your information is correct, you will be sent a verification email to the address you provided. It may take a few minutes for the email to get delivered. Click the link in the email to activate your account.

TL;DR in Vietnamese:
Mở trang chủ Facebook. Điền thông tin của bạn. Nhấp vào nút "Đăng Ký" (Sign Up). Mở thư xác nhận.