NGINX Usage Reporting using NGINX Agent

With the assistance of NGINX Agent, you can now effortlessly report your NGINX Plus instances using NGINX Instance Manager. This feature will enable you to manage your instances more efficiently.

[@mawesome4ever]

So in order to use NGINX and NGINX Agent, I have to install NGINX and NGINX Agent using NGINX dashboard. But if I already have NGINX how much NGINX can NGINX do if NGINX can NGINX Agent?