You can connect multiple robot heads (or any other devices) to one computer using ARC by following these steps:

1. Ensure that each EZ-B IoTiny is connected to your Wi-Fi network. You can do this by following the instructions provided in the "Connecting Over WiFi" section on the EZ-B IoTiny page.

2. Open ARC on your computer.

3. Click on the "Project" tab, then select "Add Control".

4. In the window that opens, select "Connection" and then "EZ-B Connection".

5. In the EZ-B Connection control, click on the "Connect" button and select the first EZ-B IoTiny from the list of available devices.

6. Repeat steps 3-5 for the second EZ-B IoTiny.

Now, both robot heads should be connected to your computer and controllable via ARC. Remember, each device must have a unique connection control in ARC. You can switch between the devices by selecting the appropriate connection control.

For more detailed instructions, you can refer to the "Multiple EZ-B's" tutorial in the support section on the Synthiam website.

Or the suggested is to run two copies of arc. One copy for each head.