Hi,
I recommend checking a really simple demo for using the FFT block in Simulink. You can open the demo by typing 'ex_fft_tut' at the MATLAB command window (I am assuming you are using R2016b on a Windows PC, and have all the necessary licenses).
In the example you will see that the FFT block takes frames of data (128 values at once), but in your model you are feeding a single scalar value to the block. Additionally, your signal is continuous so you will need to discretize it to be able to take the FFT with the block. One way to discretize your signal can be to use a Zero-Order hold and specify an adequate sample time. You can also use a Buffer block to create the frame of data that your FFT needs.
Please check the image below and see how I modified the example 'ex_fft_tut'. You can do something similar with your model. The image shows the dialog parameters for the Sine Wave, Zero-Order Hold, and Buffer blocks - everything else has the example defaults.
I hope this helps!
