You can upload new builds to any release channel. New builds must have a higher version number than the last uploaded build.
Uploading an app to a release channel signifies that you are ready to release it to an audience even if that audience is a group of internal testers.
The first time you upload a build for your app, it goes into the Alpha channel. You can upload subsequent builds into any release channel you want, as long as it has a higher version number than the last build uploaded to any of the channels. The version number limitation applies across all the channels because it is possible for users to belong to more than one release channel.
To upload a build:
If this is an Oculus Rift app, fill out the form and then click Upload.
The build is uploaded to the channel and is made available to all subscribed users.