If you are attaching only one appendix, label it Appendix; if you are using more than one appendix label them with a capital letter (Appendix A, Appendix B etc.) in the order in which they are mentioned in the text of your assignment.
In the text, refer to the appendices by their labels. e.g. (see Appendix A).
Each appendix should be on a separate page and goes after your reference list.
For more information and examples please consult the Publication Manual of the American Psychological Association (link below).