What spectrum analyser settings should I use

I have built a simple model consisting of a CONSTANT source, of amplitude 1 and a sample time of 62.5 us and simulation time of 500 us with an oscilloscope and spectrum analyser i.e. N=8. The spectrum analyser has been setup with HANN weighting and 0% overlap and inherited sample rate with a power spectrum (dBm).The scale is linear with 0 Hz offset and a reference load and averages of 1.

I would like to know what settings should a choose in the Main Options for RBW/Window length and subsequent sub settings e.g. NFFT etc.