All I can really discern so far is that you are a Windows user (reference to COM port).
Have you powered up tinyG? What leds are on, off or flashing?
If you are coming from another Arduino based environment (Uno, DUE, etc) be aware that tinyG is not powered via the USB cable.
Don’t get lost in the info on tinyG FW download, etc, quite yet anyway.
The USB terminator on the tinyG, that manages USB details and should cause tinyG to appear as a COM port to your PC, is hardware, not FW on the tinyG device. All you should need to bring up the COM port on a Windows PC is a powered tinyG and a good USB cable.
Until you see the COM port on plugging in the tinyG USB cable, focus on the Windows machine – driver install.
If you have a Win10 machine around, try plugging tinyG into that to see if the COM port appears. To best of my recollection, Win10 was FTDI enabled out of the box.
I’ll assume you have found the wiki at