Information on creating a Splashtop JSON can be found here under the installation files heading:
Navigate to your Profiles tab and click the plus sign under Available Payloads.
Select Android and then File
Note: In 6.2 all files must be stored under C:\Program Files\Wavelink\Avalanche\centralfilestore\files
Name your payload, select Add/update file, specify the file path for your particular device type (\enterprise\usr\persist, \persist, or \sdcard), click the search icon under File and select your file, and click Save
Your file payload will now show under Available Payloads