how can i access the percentage harmonic from fft analysis to matalb m file?

this is some information for the signal simulated in simulink , name simul;

simul=time:[5000x1 double]

signals:[1x4 struct]

input:1

signal:1

startTime:'last'

cycles:1

fundamental:60

etc

so how can i change the inputs (input 1 input 2..) and fundamental from 60 to 50 hz? and how can acces the indivudal percentage harmonic of the simulink data (simul in my case) in m file? thanks