Add a team to an Office 365 group

To add a Microsoft Teams team to an existing Office 365 group, first click Teams > Add team, then click Create a team.

You'll see a link that takes you to a list of all the Office 365 groups that you can add a team to. From there, all you have to do is select the group you want and add your team. You'll end up in the General channel for the team you added to your Office 365 group.