Hi @Berke_E ,
I have tried to replicate the steps in s32k3xx_extmode_ebt_example_readme.html, please follow along:
1. Open the s32k3xx_extmode_ebt model and go to Hardware Settings -> Target hardware resources -> Select Configuration Project Template to be S32K312-Q172 EB Tresos:

2. Then this Warning Dialog will appear on screen and click OK:

3. Then go to External Mode and select the Serial port of your board, press Refresh:

4. The serial com port must match the K312 boards OpenSDA as in Device Manager, in my case is COM12:

5. Click on Apply and OK, to close Configuration Parameters.
6. Press Monitor & Tune in Simulink, wait 1-2 minutes, then the Blue LED will toggle on the K312 board.
7. Open the Scope output and see the sinusoidal shape:

These steps are from the s32k3xx_extmode_ebt_example_readme.html , that my colleague @Irina_Costachescu mentioned above,
Hope this helps,
Stefan V.