My understanding of "cover letter" is the text of your first letter, introducing yourself, what position you want to apply for and other simple information. Then you can make your resume or recommendation letter (scanned copy) into a PDF file and pay at the back. Of course, you can also write some contact information, such as phone number and email address.
In fact, it's the first time I've heard about the position and the cover letter. Generally speaking, when you submit your article online, there will be a cover letter. Don't take the position you are applying for so formally, just look for a position in China.