On what grounds are you appealing?
You normally cannot appeal on the grounds of academic judgment i.e. you disagree with the mark you got. Normally you can only appeal on procedural grounds e.g. you were told you had 2 weeks to complete and assignment and it had to be turned in within 48 hours, or the topics for the assignment were not part of the syllabus or something perhaps.
If you just didn't like the mark you got then there's nothing you can do except reflect on the experience and identify where you went wrong and how you can improve for the next one.
Nothing you can write will change that.