To install UrlParams just go to addons.mozilla.org or to the Download page
and download urlparams.xpi.
Then drag the file into Firefox or choose File->Open.
For Mozilla / SeaMonkey Users:
After installing UrlParams and restarting the browser, go to Tools -> Addon Manager -> UrlParams -> Preferences and hit the "Install Sidebarpanel" button.
Note:
As there is no uninstall feature implemented, uninstalling UrlParams after using the "Install Sidebarpanel" button,
involves some manual editing of profile files (uninstall via addon manager and remove all occurences of UrlParams in >your-profile</panels.rdf).
Or.. you use xSidebar for adding the Sidebar (this is done automatically after installing both extensions).
How to Install