Try to organize and centralize the uploaded files into one folder that is named '_downloads' on the Home list of your website. It makes it easier later to find it faster. There could be occasions that you rather upload a file to somewhere else.

Navigate to the '_download' folder under the Home list of the website.(or any other location you want to upload the file/s to)
Locate the 'Upload' button on the top right of the page.
Notice the elements of the next window.
1. On the top of the window, it tells you where you are uploading the file to. In this case we are at the 'Home/_downloads'( that is the same as '/downloads')
2. Type:
  1. Upload Files: it lets you select multiple files in one shot.
  2. Edit and Upload Image: it lets you to do basic edits on the image before upload.
  3. Import Zip File: it lets you import a Zip file. The zip file will be UNZIPPED as it uploads.
3. Left the other options as they are.
Click +Add and pick the file/s you need to upload.
The list of file/s will appear on the bottom of the window.
Click 'Start Upload'.
Don't forget to publish the uploaded file/s.

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