Your calendar in Teams is connected to your Exchange calendar. In other words, when you schedule a meeting in Outlook, it'll show up in Teams, and vice versa.
There are several ways to schedule a meeting in Teams
Click Schedule a meeting in a chat (below the box where you type a new message) to book a meeting with the people in the chat.
Go to Calendar on the left side of the app and select New meeting in the top right corner.
Select a range of time in the calendar. A scheduling form will pop open.
The scheduling form is where you'll give your meeting a title, invite people, and add meeting details. Click Scheduling Assistant to find a time that works for everyone.
Once you're done filling out the details, click Save. This will close the scheduling form and send an invite to everyone's Outlook inbox.