Let's suppose you want to write file name myfile.extension
in folder myfolder
then your upload path will be:
<root>/myfolder/myfile.extension
then your endpoint url to upload file will be:
https://api-content.dropbox.com/1/files_put/dropbox/myfolder/myfile.extension
In case of download you first need to send request to endpoint:
https://api.dropbox.com/1/media/dropbox/myfolder/myfile.extension
In response you will get json like: {"url":"here is downloadable link"}
To see contents/details in folder, endpoint will be:
https://api.dropbox.com/1/metadata/dropbox/hello?list=true