The appeals process will not challenge an academic decision. It is up to the academics to make academic judgement regarding grades. You cannot appeal solely because you disagree with your grade. You can only write an appeal if you are concerned that there were irregularities in the process or that the process was not followed. This arises where the University is satisfied on the basis of evidence produced by the student or derived from any other source that the assessments were not conducted in accordance with the relevant Regulations, or that a material administrative error or some other material irregularity occurred in relation to teaching or assessment (including project and placement units), such that assessment performance was materially and adversely affected.
If you don't understand why you failed you should seek feedback from your tutor in order to clarify this. You can also refer to the University Regulations and Quality Assurance Handbook available on the main University website in the Regulations section for clarification on University marking/grading process and systems which are in place to ensure this process is fair. The Students' Union can provide advice and also representation when making an appeal. Come and find the BedsSU office on Level 1 of the Campus Centre in Luton or in the Hub in Bedford, or email them at email@example.com.
Forms can be found through the following link: www.beds.ac.uk/student-experience/academic-information/academic-appeals-policy