The Quack Toolset is a so called userscript. With userscripts you can manipulate pages on which you are currently surfing to change for example the way they look or how the interface can be used.
Only a few steps are necessary to be able to use userscripts and this toolset.
Depending on which browser you are using a certain addon must be installed first.
You probably have to restart your browser after the installation.
The official download is hosted by OpenUserJs. I visit this website on a regulary basis to answer questions or comments.
The download on Greasyfork is used as a mirror in case that OpenUserJs is not available.
Other than that I'm active on Github. Everybody who has written an extension or bugfix for the toolset can submit their contribution here. You can find Beta versions and other experimental versions here, too.
In case that Grepolis was opened during the time of installion you have to refresh the page (press F5).