The upgrade of firmware is always performed through USB. The first step is to get the file you need to download the firmwware tool for the controller. This can be found on the product website under 'Downloads/manuals'.
Next, please check that the 'skip bootloader' jumper JMP1 is not placed on the board.
When you connect the controller through the USB cable with the PC the board will first start with toggling LED2 and LED3. It will do this for around 5 seconds. This toggling indicates it is in a so-called bootloader modus, which is the modus it needs to be in order to be able to connect to the firmware upgrade tool. After this 5 seconds it will continue to start the 'normal' controller firmware. If jumper JMP1 would have been placed it would skip this 'bootloader' step.
If you for any reason are too late with connecting with the bootloader upgrade tool, simply remove the USB cable and try again.
First, remove the USB cable for now and start the firmware tool. It will, of course, indicate that it can not find the controller.
Next, connect the USB cable and immediatly click on 'Get Version'. As result, it should have connected to the board by showing the text 'BL CPU5A V2.00' or similar. Also, it will report 'Device attached'.
Now it's time to load the firmware file you want to upload to the controller. Click on 'File' and browse for the firmware file that you have downloaded. In this case 'cpu5a_usb_v111.cry'.
Depending on your controller you might need a different firmware file, eg. for the CPU5A4E you need the ethernet firmware.
The final step is programming the controller by clicking on the 'Program' button.
When programming was successful close the software and remove the USB cable. Optional you can place the JMP1 jumper back. Now re-attach the USB cable, and start the CNC software it should now indicate a different firmware version.