How you cite your own work depends on what it is, and whether or not it has been published.
Published work
If you are citing a published work, you cite it as per normal for the work (e.g., photograph, book chapter, etc). For the citation (both in-text and in the reference list) you refer to yourself by name just as you would any other author. When discussing your work in-text, the general convention is to talk about yourself in the third person, but make it clear that it is your own work you are discussion:
Previous research undertaken by this author has shown... (Bloggs, 2018).
But it may be appropriate to refer to yourself using first person pronouns, particularly if you are writing a reflective piece, so check with your lecturer.
In my previous research I found... (Bloggs, 2018)
Unpublished work
If the work can be found or sourced online by the public, it is informally published and should be treated as a web page. If it cannot be found by the public and can only be accessed by people who have been given access to the private link or sent a copy in person, then it is an unpublished work.
Photographs, illustrations, art
Unpublished photographs and works of art created for the assignment (or appearing only in the assignment/paper and no where else) are not cited - so they do not have a formal in-text citation or an entry in the reference list. Treat it as a figure, and add any necessary details in the Note section under the image.
Add "Own work" to the image if you feel it needs to be made clear that this is an image you created yourself.
Figure 1
Hong Kong before 2019/2020
Note. Photograph of Hong Kong taken in early 2000s. Own work.
If you are using your own image for an illustration in a PowerPoint presentation, you don't have to cite it, but you can put "Own work" on or under the image somewhere unobtrusive if you wish to avoid confusion.
When referring to your own artistic work in text, you need to make it clear that you are talking about your own work, but you do not cite it.
Previous assignments
Assignments submitted for other subjects are regarded as unpublished manuscripts, and are cited as such.
Reference list:
Bloggs, J. (2020). Lancelot does not deserve your love: Critiquing the "heroes" of Arthurian legends [Unpublished assignment submitted for EL1006]. James Cook University.
In text:
(Bloggs, 2020).
However, your past assignments are not usually considered to be a scholarly source, and most lectures do not want you to cite your previous assessment. You should only refer to past assignment work if you have been explicitly asked to do so (e.g. for a reflective assignment).
It would be much better to update your research and conclusions from the past assignment (and use new words to express your thoughts) than to refer to it or cite it.