When you are in Teams, on the left side, you can see Teams as a link. If not, click on the 3 dots and there should be an icon for Teams.
Then, there is a link on the right side to Join or create team
You will want to make someone else the owner of the Team and you can have multiple owners. That way, they can add or remove members as needed. On the top of your new Team, there is a File section for where you can add files but you would click on the link to Open in Sharepoint first.