The documentation from Applied Biosystems is ok.

You set up a "standard curve" of at least 5 concentrations of your template. You use the slope of the graph of ct value vs. log of copy number to calculate the efficiency. Check out Thermo Fisher's website for more information.

https://www.thermofisher.com/us/en/home/life-science/pcr/real-time-pcr/real-time-pcr-learning-center/real-time-pcr-basics/efficiency-real-time-pcr-qpcr.html#curve

I suguest use Primer Blast online software of NCBI website along gene runner offine software.

You can use Primer Blast online software of NCBI website.

I suggest use use positive sample or positive control for that primer set

I agree with @Katie A Burnette. You can also use the melt curve data for different concentrations of template to check whether the primer binding is affected in different concentrations or not.

Thank u all. I have check suggestion given by Dr. Brunette.