Article in English: You will find this bar on the upper left-hand corner of your home page. Facebook’s search bar is designed to help you find a specific person, even if you don’t know their last name. The search results are based on the information you have included in your profile. Once you begin typing, Facebook will start generating results for the most likely query based on your profile information. Facebook is more likely to suggest friends who are from your own city or country, or who share the same college or workplace. The more details Facebook has about you, the more fine-tuned their search will become. If you can't find your friend with just their name, include the name of their city, college, workplace, etc. This may narrow down your results. If you know your friend's email address, you can also type this information directly into the search bar. Their profile will only appear if the email address you typed is the one they have associated with their Facebook account. Once you have found the right profile, click on it and navigate their profile page to the “Add Friend” button toward the top to send them a friend request.  If this person is a new or long-lost friend, or someone who you haven't seen in a while, it is considered polite to send them a message along with your request. Help them remember who you are, so they don't deny the request by mistake.

Summary in Vietnamese:
Di chuyển đến thanh tìm kiếm của Facebook. Gõ tên của người cần tìm vào thanh tìm kiếm. Thêm thông tin liên quan. Gõ địa chỉ email của người cần tìm vào thanh tìm kiếm. Kết bạn với họ.