Please ensure you are using you're shool username and password.
There is a mail icon on the desktop. This will take you to the web app
Contact support through the live support link.
The link below takes you to a page that has videos to help you use Microsoft Teams. Very useful and easy to understand.
When working from home, you should always have a USB stick in you're laptop. Attachemnts need to be saved to USB before you can open or work from them.