Visitors to Vietnam must obtain a visa.
You just need to fill out the visa application form online. (below there is a link to an online visa service agency)
The Online visa application does not require sending your passport.
You get a visa approval letter issued by Vietnam Immigration Department indicating that you are allowed to enter Vietnam and have your visa stamped upon arrival at one of Vietnam international airports (Tan Son Nhat Airport in Ho Chi Minh or Saigon City, Cam Ranh Airport in Nha Trang City, Da Nang Airport in Da Nang City or Noi Bai Airport in Hanoi Capital of Vietnam).

All visitors must hold a passport valid for 6 months.
Getting a visa takes usually 4-7 business days. If an urgent visa is needed, it’s possible but visa service agencies ask more money.

Visit this link to visa service agency or search for a visa agency in your own country.