There are 2 options to install the Clirr plugin in an existing Maven installation:
maven plugin:download -DgroupId=clirr -DartifactId=clirr-maven -Dversion={version}
where {version} is the version to use. Maven will
automatically download the plugin and install it, uninstalling any
other version you may already have.
{MAVEN_HOME}/plugins where {MAVEN_HOME} is
the location where you have installed Maven. Make sure you also
remove any previous Clirr plugin from
{MAVEN_HOME}/plugins and delete your
{USER_HOME}/.maven/plugins directory.