1) In a "harmonic problem", you can often measure the frequency at which the "problem" occurs. If this is the case, then you specify this frequency as the "starting frequency" and leave the "ending frequency" and "increment" blank. If on the other hand, you only knew the frequency approximately, then you could specify the "starting frequency" as 90% of your approximate value, the "ending frequency" as 110% of your approximate value, and the "increment" as 1% of your approximate value. Then review the results to see which frequency generates the results closest to what you experience in the field. Go back and change the frequency values to further narrow things down until you find the exact frequency you need.

2) Typically you can't measure a harmonic force. Usually the "harmonic force specification" is used to "simulate" (or guess) at the load causing a problem. Once the specified force correctly "simulates" the problem in the field, you can then adjust the model so that it doesn't respond to this load.

3) The "Load Cycles" specification is used only for fatique analysis. It is the anticipated number of applications of this load (or displacement) on the system. "Harmonic Displacements" are a measured value.