At this point, the Kepler - Attachment fields | simple & multiple custom field is ready to be used as follows:
Step 1: Click on Attach file Icon 
to select a file.
Step 2: Choose a File from the opening window.
Step 3: As depicted in the screenshot below, some information about the uploaded file is available:
...
3. Preview images or save the file.
PS: When users attemp to attach empty files to an issue an "Empty File Warning" appears, the attachment process is not blocked so users can proceed as needed.
Screenshot below shows an empty file "Exemple.txt" . Empty means the size is 0 KB.
Step 4: The Kepler - Attachment fields | simple & multiple Manager controls automatically the attachments according to the administrator's configuration and displays error messages in case of files that do not correspond to the field configuration.
Case Case 1: The file extensions are different from the configuration.
Case 2: The file size is greater than the defined one.
Case 3 : The attached file is empty ( file size equals 0 KB) differently from the configuration.
