I am trying to setup a generator spec file; the details I have is that: Fuel consumption 2,4 L/Hr / Fuel price 3,6 Rand / O&M cost 0,5 (Rand/kWh) / Rated Capacity 8 (kVA) / (plus some other details that I can see where to put).  How would I "translate" the above info so it matches the various HOMER input fields (eg. capacity in KW/hr)?

Let's assume a power factor of 0.9, so an 8 kVA generator would put out 7.2 kW at full power.  So we'll specify it as a 7.2 kW generator.  I'll assume the O&M cost is for full power operation when you are producing 7.2 kWh/hr.  So at 0.5 R/kWh, that's an hourly cost of 3.6 R/hr.  HOMER assumes the O&M cost is independent of the power output.  I'll assume the capital and replacement costs are 30,000 Rand.  Here's how I would enter this in HOMER:

You didn't specify the fuel but I'll assume it's diesel.  Switch to the Fuel tab, choose Diesel from the fuel type drop-down box, and click the Fuel Curve Calculator button.  All you have is full-load fuel consumption, so I'll assume that its fuel consumption at zero output is 25% of that at full power.  So here's what I would enter:

That's a reasonable looking efficiency curve.  When you click OK HOMER will copy the calculated values of the fuel curve intercept and slope into the appropriate windows on the Fuel tab of the Generator Inputs window.  Click OK to that window too.

Now for the fuel price.  Click the tab labeled Diesel.  All you do here is enter the price.  I assume the price you gave is per litre.

That should do it.