I think that you should start the calculations from the generator.
Let's say your generator output has to be 300W at 250 RPM.
Go tho that spreadsheet and input 300 in the cell "C6" and 250 RPM in the cell "C7".
All the other cells will be updated automatticaly with values calculated based on your input.
C9 suggests you the diameter value. Insert this value in "C10" and you just got a set of values for your blades in rows 26 to 45. You don't have to modify any of the other values, but, if you want you can play around with them.
You can modify the TSR, the number of blades, or gearing ratio to see how that affects the size of the blades, but I sugest to stick with their default values unless you know exactly what you are doing.
So, find the output and RPM for your generator, insert them, get the suggested diameter, insert that value, and you got your blades pattern.
To find out your generator output, spin it at different rpm's and measure the volts and amps with some load, then find the power P=U*I for each RPM measurement.
Have Fun,
Speo