Step 1 - Open Teams, in the navigation bar, click the Teams icon.

Step 2 - On the Teams page, click Join or create team.

Step 3 - Click Create team.

Step 4 - Choose a template for your team and click Use this template.
              Note: Refer to Teams: Choosing a Team Type

Step 5 - Click Create team. 

Step 6 - Choose a privacy level for your team, either Private or Public.

Step 7 - Give your team a name and a detailed description and click Create.

Step 8 - Add members to the team by typing a name, distribution list or security group. You can also add people outside your organization as guests by typing their email addresses. Click Add. Your team will appear in your teams list.

Step 1 - Access your Team, click More options ... > Manage team. 

Step 2 - Select the Members tab.

Step 3 - Find the people you want to designate as team owners. Under Role, select Owner. 

Step 1 - Access your Team, click More options ... > Add channel. You can also click Manage team and add a channel in the Channels tab. 

Step 2 - Choose a descriptive Channel name to make it easier for users to understand the purpose of the channel. Explain more in the optional Description field if desired.

Step 3 - Choose a channel type from the drop down.

• The default is Standard to create a team that all team members can view and participate in. 
• Private creates a channel that only select members of the team can see. See separate instructions for creating a private channel. 
• The Privacy option cannot be changed once a channel has been created.

Note: 
Team owners can automatically favorite channels for the whole team, making the channels more visible for everyone on the team.

Team owners can also pin tabs to the channel to add tools, such as OneNote, links to webpages, and other content to make it easy for users to find what they need and share their thoughts.

See Microsoft's page on working in channels