GO TO THE MANUALS/TUTORIAL OF FiSAT II, WHICH IS AVAILABLE IN UPPER RIGHT SIDE CORNER. It is simple enough. 

Fishing mortality can be calculated based on Z (estimated by  Length converted catch method in FiSAT II) subtracting  M (caclulated by Paulys empirical equation). Fopt can be calculated using selection ogives method.

You can have at Derek Ogle website.

http://derekogle.com/fishR/

I think you can find what you need but you also need to be able to work in R.

I think this can this be done by probit analysis.

SEE THE ATTACHED REFERENCES. THEY ARE LIKELY TO HELP HOU