You wish to import groups (ie teams, classrooms) for your event. This feature can be used for any type of event where teams are predetermined and is common for school events in which all students register under their classroom group.
From your admin area, go to People -> Groups and click Import Groups. Note that your file must follow the formatting of the example Microsoft Excel file found there to successfully upload. If you do not wish to include some information you may leave that column blank. However, do not delete the column! Also, imports are limited to 100 groups at one time. If you have more than 100 groups to upload, you must do this in multiple uploads.
Fields that can be imported include: Team Name and Team Number. The Team Name field appears on registration and search pages, so this is the primary field that your constituents will see. In addition, if you are importing participants, you can assign the Team Name as part of the import. The Team Number field is an optional field that can be used for ordering your groups.
Once you have your data in the worksheet, save it. Then, browse to locate the Excel file on your computer. Once you have attached the file, hit 'Import'.
If you are importing Groups and Participants, you should import groups first. You may then associate your participants with a group via the Team Name field in the Participant Import. Note that team fundraising pages will not be created via the Group Import. They are generated via the team captain's log-in. See also this article for full details on uploading participants.