The name of the file should be plugin_rcpuserdel_1.0.tgz. To install the plugin take these steps:

1. Log in to the administrator back-end of Joomla
2. Click on Extensions → Install/Uninstall
3. Browse to your local file
4. Click on “Upload File & Install”

The plugin is now installed but not yet active. To activate and configure the plugin take these steps:

1. Click on Extensions → Plugin Manager
2. Click on System - RCP Userdel
3. Set Enabled to Yes
4. Fill in the settings to your wishes
5. Click on Save

The installation is now complete.