There are too many add-ons and third-party products to expect us to know them all, so you might provide a link to provide context.
Also, as this is a general Alfresco forum you probably should be asking the developers of the third-party product how to do the install.
With that said, hopefully your add-on was provided as an AMP (Alfresco Module Package). Typically there are two: One for the "repository" tier and one for the "share" tier. Copy the repository (sometimes labeled "platform") AMP into /opt/alfresco/amps and the Share one into /opt/alfresco/amps_share (where /opt/alfresco is your Alfresco install directory), then run /opt/alfresco/bin/apply_amps.sh.
More on installing AMPs can be found in the docs.
