Step 1: please select a file by pressing the bellow button "Choose file". To add more files, press the button "Add file" and you will see another option "Choose file" available.

Step 2: After you select the files, press the button "Upload"


Step 3: To see the uploaded accepted files, press the button "See uploaded files"


If you select and upload wrong files, you can delete them one by one or you can press the button "Delete all" and start the process again.