You have downloaded a "jar" file containing the plugin.
Use bitegarden UPM to install the plugin directly from the administration user interface or copy jar file into SonarQube™ plugins folder:
Restart SonarQube™ server and enjoy the new features.
Commercial plugins include an embedded trial license for two weeks for evaluation. You don't need to setup anything.
Depending on the plugin you might need to run a new analysis to compute the data.
You will find main features for the plugins under the "More..." section in global or project spaces menus