The Scottish Government has written guidelines on completing the MCCD in publication SGHD/CMO(2018)11.
You should have covered the basics of writing an MCCD during induction and training. If there is any doubt on how to complete a certificate you can ask for senior help. Further it would be wise to read the guidance above, as well as the NES page on MCCDs. The National Records of Scotland also has more information on MCCDs.
Remember, these are legal documents and must be completed correctly and concisely. If still completing a paper form, you should use block capital letters with no abbreviations and no scoring out of causes of death.