On Biteable 1.0, you can upload short, 2.5 - 30 second clips to Biteable but only on the premium account. Once you're premium just click Add Scene, select Upload > Video, pick a scene to upload the clip to, then upload. It will only take the first 30 seconds of your clip and won't import the sound.
On 3.0, you can also upload your video as a Background footage. Check this article out to get going!🚀