I'm not sure what you'd like to achieve. `nxlog.conf` is the main config file, where you define sources of your logs, the way of handling them, and targets where logs should be forwarded.
I recommend spending a while on analyzing the documentation (I assume you're interested in the community edition): https://nxlog.co/docs/nxlog-ce/nxlog-reference-manual.html. You can find many examples of configs there - I believe that's the best starting point.
Once you find what's interesting for you - solving any issues would much more feasible.