Your child has been set up with an Office 365 account. By logging in they will be able to access Microsoft Teams for their daily live lessons and complete assignments. All your child has to do is log into their Office 365 account where they’ll have access to Microsoft Teams. Microsoft Teams can be accessed online or downloaded to a home or mobile device.
Here is a demonstration of how to use Microsoft Teams by Mr Khan.
Here is a video explaining how to join and rejoin a meeting.
This video explains how to use multiple Teams accounts