InstantRig is a dynamic panel. Different rollouts and buttons will be enabled or disabled depending on which part of the rig is selected in the viewport. 
Start pressing the “Create Root Node” button. It creates the main root controller of the rig. When the root controller is selected, the “Hub” button will be enabled in the “Create Module” tab. continue creating the first hub bone. If the hub bone is selected, different module buttons will be enabled in the “Create Module” tab. Then you can continue creating different modules top of the hierarchy.

The script can be launched from the button InstantRig available under the App Store Menu. If you are unable to find the menu, then please reset the workspace and restart the product.

The installer that ran when you downloaded this plug-in from the Autodesk App Store has already installed the plug-in. You may need to restart Autodesk Product to activate the plug-in.

To uninstall this plug-in, click Control Panel > Programs > Programs and Features (Windows 7/8.1/10/11) or Control Panel > Add or Remove Programs, and uninstall as you would any other application from your system.