I need to make a statutory declaration (Akuan Sumpah) to complete (Lampiran A.15(2)). How do I go about doing this?

You need to make this statutory declaration in front of a Commissioner of Oaths. If you are applying at JPN Putrajaya, there is a Commissioner of Oaths located on the ground floor of JPN. You can take the oath with your husband there before proceeding with the citizenship application. If you are applying overseas, this can be done at the Malaysian mission.