Your username for all things google (sheets, docs, drive, etc) is your email address and password. 

Your work issued email address is first name followed by a period and your last name, 

(Ex. your password is the last 5 of your student ID number + the first 3 of your last name (Ex. 12345Dou) 

If you cannot login to gmail with the default username and  password, please reach out to your teacher or guidance counselor who can submit a request to IT