Where did your 10 seconds of history data come from? A sensor on a physical structure or from a simulation?
Stress is a result, not a load. The History Data is a multiplier on the loads applied in the Static Structural model.
For example, if you had a load cell measuring the fluctuating force going into the end of a cantilever, and the units were measured in kN, then in Static Structural, you would apply a 1 kN load at the end of the cantilever, and read in the measured data using History Data. Those numbers in kN will multiply by the 1 kN load case to obtain the stress at each moment in time. Rainflow counting will extract the fatigue cycles, binning the number of cycles by amplitude of stress, then it will sum up the damage using Miner's Rule and present you with a Life plot.
This rainflow counting of fatigue cycles is far more accurate than just taking the RMS value because the damage done by a few peak amplitude cycles can be much more than a larger number of cycles at the RMS value.