You can get into Microsoft Teams in two ways: via the Office 365 or via the Microsoft Teams desktop app. Let's look at both ways in detail.
How to get into Teams
Getting into Teams via Office 365
When you log into Office 365, you are automatically logged into the online version of Microsoft Teams. Others can see your presence and contact you:
You can see your contacts and IM them when you go to Microsoft Teams via the app launcher, or on Office 365 Home.
Getting into Teams via the app
Once you download the app, you can sign in. You can download the app from Microsoft...