You need this to get it done:
Action DetailsRequirements and how-to articles for Instagram's action:
iOS, Android or Windows Mobile Device
In order to upload videos onto Instagram, you need to do so using a mobile device via the official Instagram app.
A caption can be added to the image you uploaded (maximum of 2,200 characters.) Hashtags can be added by adding a word prefaced by a "#" which allows people to discover your image(s). (For example, an image with "#fashion" in its caption will show up for everyone browsing the "fashion" tag.) (maximum of 30 hashtags)
Video to be posted. Either uploaded from the phone's library/gallery or recorded in the moment (up to 60 seconds long.)