This plugin is delivered with the NopAdvance Core plugin on which this plugin is dependent. You need to install the plugin using the plugin installation guide provided here.

Once you have installed plugin, you will be able to see the plugin menu under NopAdvance > Plugins > Admin layout changer in your nopCommerce admin menu, similar as displayed in the below image.

Click on the Configure menu item from Admin layout changer plugin menu as displayed above and you will be re-directed to the plugin configuration page.