You could start uploading files by clicking the "Upload" button on the top right
Click "Select File" to browse your file and click "Upload File(s)" when ready. You could upload 4 files at a time. If you need to upload more files, just close and relaunch the upload page.
Make sure you see the text turned to green "File Uploaded Successfully" before you close this upload page.
You will see the files being uploaded to the order.
You could download the files by clicking the file name.
You could start upload files once you have created an order. There is no size and file limit to your upload. You could upload 4 files at a time. If you need to upload more files, just relaunch the upload form.
Once you have uploaded your files, you could download it from anywhere with an internet connection and browser.