If you've been invited to Teams as a Host or Company Admin, you will receive an email that requires attention. It will be sent from email@example.com.
Click the hyperlinked "Follow the link" and you will be redirected to Teams to choose a password for your account. It must be at least 8 characters, have at least 1 capital letter, and have at least 1 digit.
After you have chosen a password that meets the criterion, you will be redirected to the company view page. You will immediately have access to Teams at the level your company admin has assigned.