1) Important things for students to understand about digital citizenship: Plagiarism - what is it and how to avoid it, how to use citations and give credit for material.
Online Harassment: what is it and steps to take if encountered.
Copyright: general understanding of people owning the rights to their original material, how to respect those rights and the property of others, how students can have copyright of their own original material.
2) Atomic learning is a source I would use for instruction.
3) teaching digital Citizenship: I would give students specific links to information in Atomic Learning, require at least one source there and encourage exploration of other sources, research and report on what they have learned-areas of citizenship and how to apply.
4) Sharing digital citizenship with parents: send a note home with the report each student created explaining the project, ask parents to read and discuss the report with their students.