Complex sentence: Teachers have the option to attach files to the assignment which students can view, edit, or get an individual ate files and then attach them to the assignment if a copy of a file wasn't created by the teacher.
Split into simpler sentences: Teachers have the option to attach files to the assignment which students can view, edit, or get an individual copy. Students can create files and then attach them to the assignment if a copy of a file wasn't created by the teacher.