Before submitting your laboration you need to upload your files. Copy all files to a directory, for example lab1, and create a tar-gz archive of the directory.
Upload this file in the Fire system.
$ tar -zcvf lab1.tar.gz lab1/
$ gtar -zcvf lab1.tar.gz lab1/
You can now browse and select the file you want to upload.
You now see the file you have uploaded and all members of your group can download or remove it.
The background color has changed to red to alert you that you need to press the Submit button to actually submit the laboration for grading.