Clicking this link will lead you to a white jpg image with grey type on it.
Download this file. It’s a 1920×1080 jpg that you can use as a template for all your homework uploads.
Make copies of it, or make a new template out of it with your info (name, etc.) already in it. When you upload, change the name for each new file. Always use a unique name for each file. If you reuse a name, you will overwrite a previous file you uploaded.
If you need to change the jpg compression to keep the file under a megabyte, feel free, but whatever you do, don’t change the pixel dimensions.
Think of it as a dinner plate. You will use it over and over for many different meals, but you would not change the size of the plate.