Generally, you can use Teams in your browser or in the desktop app. The desktop app is available for Windows and for MacOS and Linux. There is also an app for Android and iOS. We recommend using the desktop app since the browser version does not support all features. These are available at https://teams.microsoft.com/downloads.
In the official Microsoft manual, you will find an overview on the basic features of Teams. Here you will also find further information as written instructions or as video tutorials.