The preferred method is installing via GIT.
Install the package with GIT:
$ git clone https://github.com/cited/Tomcat-Webmin-Module $ mv Tomcat-Webmin-Module tomcat $ tar -cvzf tomcat.wbm.gz tomcat/
Upload from Webmin->Webmin Configuration->Webmin Modules
Go to Servers->Apache Tomcat (you may need to refresh page)