Hi Sofien,
I have attached an example file of using an electrical equalizer to compensate for dispersion in an optical link. I believe it answers all of your questions, although if you have written your own Matlab code for an electrical equalizer your solution could be different.
To define a training symbol you can use the Pseudo-Random Bit Sequence Generator or User Defined Bit Sequence Generator. To connect it to the Matlab component, just add another input for your device. In the Inputs tab change the Number of input ports from 1 to 2. You can then use a fork like in the example.
Let me know if this helps!