From the Start screen, swipe left to display the Apps list.
Alternatively, tap All apps (located in the lower-right; may require scrolling).
Tap new (located at the bottom).
From the "To" field, enter a 10-digit mobile number.
Alternately, enter a contact name. As the name is entered, a matching contact may appear and can be selected at any time.
Alternately, tap the Plus symbol (located in the upper-right), tap a contact then tap the appropriate mobile number (if applicable).
Repeat this step as necessary to add additional recipients.
From the "type a message" field, enter a message.
Tap attach (located on the left; above the keyboard).
Tap the appropriate folder (e.g., Camera Roll, Saved Videos, etc.)
Tap the desired video(s) then tap Done.
Tap Send (located on the right; above the keyboard).