Tap the icon with the downward-pointing arrow, in the lower-left corner of the screen, to save the Snapchat video to your Memories gallery.  Tap the Mute icon in the lower-left corner to save or send your video without sound. Access Memories by swiping up from the camera screen. Saved videos can be downloaded to your device or shared with other apps by tapping a video and then tapping the Share icon in the lower left corner. Tap the square icon with the "+" symbol in the lower-left corner, and then tap Add, to include the video in your Story.  Your Story is a collection of Snaps that you've taken and added over the last 24 hours. Friends can view your Story multiple times. Snaps older than 24 hours automatically disappear from your Story. Tap the Send To button in the lower-right corner. Check the box next to one or more friends who you want to share your video with, and tap Send in the lower-right corner.  You can also add the video to your Story by checking the box next to My Story before tapping Send. If you'd like your friends to view and reply as a group, rather than individually, you can create a group by tapping the Group icon in the upper right corner after selecting two or more friends.

TL;DR in Vietnamese:
Lưu video. Thêm video vào Story. Gửi video cho bạn bè.