The first thing to do is to enable Tag Meta plugin. To enable the plugin go to menu "Extensions" -> "Plug-in Manager", find a system type plugin named "System - Tag Meta Community" or "System - Tag Meta Enterprise" in the plugin list, and click on it to access to plugin settings. Set "Status" to “Enabled”, and set other parameters on the right side according to your needs. Look at "Plugin settings" paragraph for detailed information about each parameter. Click on "Save & Close" button and check that the plugin is now enabled.
Remember that is the plugin that "does the work". The Tag Meta component is just the administrative interface for managing meta rules an other features, but is the plugin that checks site requests and performs meta enhancement when needed. So, the very first thing to do is to enable the plugin. Note that if you need to disable Tag Meta, just disable the plugin.
Another thing to check is the plugins order that can be very important, especially if there are some other plugins that mess with page's meta information. In most cases it is better to set Tag Meta as the last system plugin, so it will be the last to be executed and to madofy page content. Now Tag Meta is ready to work! You can now create your first meta rule, and test the result through the web browser. Be careful that you could get a cached page. To avoid this just clear server-side cache from backend (menu "Maintenance" -> "Clean Cache"), and client-side cache from your web browser.