Below are instructions for breaking up a file in WinRar:

1. Select the file you want to add to an archive. You can do this from right-clicking the file, selecting the WinRar menu, and choosing “Add to Archive.”
2. In the “Add to Archive” dialog, find the text “Split to volumes, bytes:” on the bottom left side.
3. In the drop-down below the text, select and type ‘2GB’ (or ‘100MB’ if you are uploading directly to Gamma webserver).
4. Once you hit OK to create the archive, the archive will be created as multiple files.
5. Upload each individual file, which will have been created as filename.zip.0##.  The ## will be incremented for each chunk.