You should be able to see the tags module on the edit page for any post. Did you check the screen options tab to make sure the tags module is selected? You could also check to make sure the module isn’t closed. If you click on the arrow next to a module on an edit page, it will open or close the module and closed ones can be hard to spot sometimes.
In the newer version of WP you need to go to the screen options and select custom fields to be visible. Once you do that, you can create your custom fields that work with this plugin. It works for me using 3.3.1.