From the Add-ons Menu choose Classroom Manager then choose Start
When you choose Start, this window will open with a message about using the add-on. When you press Start the add on will create several sheets in the current spreadsheet. When it has finished select Close to close the window.
The add will create the pages listed below. You can get more details about each of those pages by clicking on the page name
gsfeCls - Will show a list of the classes currently in Google Classroom
gsfeTchrs - will show a list of the teachers attached to the classes listed in gsfeCls
gsfeStdnts - will show a list of the students attached to the classes listed in gsfeCls
sisCls - Will hold a list of the classes imported from your School Information System.
sisTchrs - will hold a list of the teachers attached to the classes listed in sisCls
gsfeStdnts - will hold a list of the students attached to the classes listed in sisCls.
You can import data from a CSV file into the 3 sheets listed above.
OtherStaff and OtherStdnts are used to hold details of teachers and students that you want to include in Classroom but aren't included in the information taken from the school information system.
ClsRmTchrs - will give a list of users listed in the Classroom Teacher group and therefore able to create classes and be added to classes in classroom as teachers. The add on will allow you to add to this group and to remove users from it.
SyncLog - if you schedule the add-on to sync this sheet will track the various stages of the sync