Using OpenResty with previously installed nginx?

As we need to log response body at certain cases, ngx_lua module seems the solution, but, then, we found that we need to install OpenResty, which has a different NGiNX binary, and not related to previous installed NGiNX.

How smooth it can be to fully migrate previously installed NGiNX settings to a OpenResty? Or use ngx_lua inside the current NGiNX server?

I searched and did not find any useful resource, official docs on OpenResty do not discuss such a case, when NGiNX is already running and has active settings, how can we use those same settings while using OpenResty? what’s the recommended way?