I also had the same issue at first but I have found the solution...
Download the following RAR file from the link below;
Once downloaded, extract these and copy the content within the "update" folder (not the "update" folder itself just the content inside it)
Paste content to the following path on your computer...
Restart Arduino IDE Software
Open Arduino IDE, select your COM port if required and Select your WAVGAT board type (WAVGAT boards are at the very bottom of the board list)
Hope this helps