First, you should use the Admin -> Addons link and try to install it directly from the marketplace - that is the best way to install addons.
Secondly, if you can't do that because your server is firewalled away from the internet, then yes, download the jar, but why have you unpacked it? Jars are distributable files, ready to be run or uploaded into their host systems - try Admin -> Addons -> upload addon and feed that the location of the .jar you downloaded.
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