Once you have logged into Teams, in the bottom left corner there will be a list:
Topics, Training, What’s new, Suggest a feature and Give feedback.
If you select ‘Topics’ there will be a lot of information about using Teams.
Specifically, if you scroll to the bottom and look under the heading ‘Support & training’ there will be a hyperlink on ‘Training for Teams (free)’ which has a lot of useful video links.