If you shared your video to Facebook, you may have received a notification (through email or Facebook notification) saying that your video was not posted due to its copyrights:
However, if you made your video using music from the Magisto library, don't worry. Simply proceed and click on "Post Video", as Magisto has the proper permissions from the owner of these music tracks.
In the following screen, click on "Post Video" again:
Important note - please make sure to share your videos directly from Magisto using the share feature (there's no need to download them to your device and then upload to Facebook)