The referencing style that all health students must use is Harvard which sets out what must be included in a reference, and the order things must appear, in order for the reference to be acceptable.
The purpose of a reference is to give credit where it's due in relation to the work of other people that you've used in your assignments. It shows that you've engaged in wider reading, that you've looked at up to date material, and that you're not passing other people's work off as your own.
The link below is to Cite Them Right Online, an electronic referencing guide that shows you how to cite a particular item (e.g. article, print book, eBook) in the body of your text and then how it should look in your reference list at the end of your work.
Do your references as you go along as this will save a lot of time and frustration later. Referencing is not optional.