Within the game at the character selection screen, click on "Play Cinematic" (the one with the clapboard icon at bottom left):

Then your desired video
- "Hope" = Republic
- "Deceived" = Imperial
- "Return" = Intro
If you want to watch the videos outside of the game on your computer, you can use RAD Video Tools to play the .bik
files in the movies directory (see below for what they're named).
The better alternative, as it's more convenient to share and replay as you can actually scrub through the video and replay bits (neither of which you can do with the above two methods), would be to just watch them on YouTube.
Intro (Movies/en-us/game_intro.bik
):
Republic (Movies/en-us/rep_intro.bik
):
Imperial (Movies/en-us/imp_intro.bik
):