You can share a channel if you are the owner or editor of that channel. Sharing happens by opening the channel and selecting the channel members tab from the navigation. Here you can click "Share to users and groups".
To share the channel start typing a team member's name or a Google group email address. Once you see the member you want to add, click their name and select "Share".
If your channel has a folder or calendar activated, Universe will also share these with editing permissions. This means that all channel members will get editing permissions by default to the Channel's Drive folder and Calendar.
You can also promote users to editors or owner from the same tab by clicking on their current role. Please note that the channel may only have one owner.