Stream Apps - upload to group or (Team) channel
At the moment the Streams app allow you to upload video's but you have no influence on where they are uploaded. The app should allow you to browse to a group or (team) channel and upload your video there.
For Android it's still not possible to upload video's to groups or channels from the Stream app.
Joe Goetschel commented
You can do this today, you link it to a Channel or a group.