The first time I tried to upload a video from my iPhone 6 into the Office365 video portal, it failed. But I tried again and this time it worked. You can add a Title and a description on the video before you upload it, and then it takes quite some time to upload just a small video on about 2 minutes. At least it worked this time, and the video is available on my portal.
It would be nice if you could decide what thumbnail you wanted to display the video with.
I have used the Spotlight feature, where you can choose which videos to display on your channel.
Go to the Video portal, and click on Portal Settings up in the right top corner
Click on "Spotlight" and select what videos you want in the spotlight areas.
One question though... how do I remove a video from the spotlight area???
Then go to the video portal again, and find the videos up in the banner of the Home page