Yeah, it's not quite "easy" I would say. It also only works in browsers which support Java, which is only IE these days.
I have done this before, and so it does work, under the right conditions. I would say, start by downloading the ZIP from the link provided and start reading the documentation contained within.
At a high level, you get new gadgets in to Finesse like this:
1) reset the 3rd party gadget account password on each uccx server via the CLI
2) SFTP the gadget files to each server via some SFTP client of your choosing (E.g., WinSCP, FileZilla, PSFTP)
3) Add a reference to the new gadget in the Finesse Desktop Layout XML in Finesse Admin
4) Login to Finesse
One helpful tip I can give you, is to create a version based folder structure. If you upload files to the server the first time, you do not need to restart anything. If you however, modify those files, you have to restart Cisco Finesse Tomcat to see the changes, and this impacts all of your Agents. So instead of modifying files, just keep creating new version folders, and upload new files everytime, changing your Finesse Desktop Layout XML to point to the new version.
E.g.,
SFTP Directory on Server
files/mynewgadget/v4/mynewgadget.xml
Then if I need to fix something in the gadget and test it, I would create a v5 folder, and re-upload all the files to v5, then change the desktop layout to use v5.
