Hi Agnese,
I understand that you would like to establish connection between EV3 and Arduino via bluetooth. Kindly refer to the steps listed in the below documentation to connect a Host Computer Running Windows to an EV3 Brick using bluetooth.
After connecting a Host Computer with EV3 Brick using Bluetooth, use 'legoev3' function to create a connection to the EV3 with MATLAB. Please refer the below documentation to know more about 'legoev3' function.