Have you taken a look at these two help articles yet? Do they answer your question?
Is your group "group staff" an O365 Group or an AD Security group?
Are you trying to add an ad security group "group staff" as members to the O365 group?
Let me explain a bit about Groups and see if that helps and if not you can explain a bit more in detail on your setup and what you tried.
Groups in Stream are based on o365 Groups. Groups have Owners and Members. O365 Groups do not allow you to have AD security groups or Distrobution lists as members or owners. You have to list individuals in the Group. However if you add members in outlook web, they have an aid that if you type in the AD security group it will auto expand and add the individual memebers. (We don't have this or member managment in Stream yet).
Once you have your owners / members in the O365 group, you can use that group to permission videos in Stream. When you upload a video or when you edit a video's permissions, use the "shared with" > "my groups" drop down to pick the group. You can make the group just viewers or also owners.
Or if you navigate to your group in Stream you can drag/drop videos to it or click the "Upload videos" button from the group bar which will default make the group an owner of the video. Or if you want to organize videos in the channel you can make a channel in the group first and then drag/drop the videos to that group channel.