Magento - Create and configure the menu
Go to Admin → System → Configuration → NEXTEND → Accordion Menu, where you can click on the Configure button, which opens up the Nextend configuration, and you can customize your menu in there.
Before the first use
Go to Admin → System → Configuration → NEXTEND → Accordion Menu
You should hit the Save Config button in this page. The module will throw an exception on the frontend, if you forget this! (The exception is also a describing message to save the config on the admin.)
Pick a category
After you picked a category, the Accordion Menu will be in the left block of your website. If you want to change that, you can find the file putting there in here: