How can i provide enough power on an UNO to use the HC-12 wireless module?
There two options I have found that work well.  

First is a simple wall-wart that provides 12 Volts to a barrel connector, like for a CCTV camera.  

Or, if I want to run the Uno from a separate higher-amperage USB charging port I have found that there are "USB A Male to CCTV male" cables that work.  

Doing the latter means the Uno is running at 5V instead of utilizing the on-board regulator to drop a higher-voltage input, which only matters if your circuit expects to find more than 5 Volts on the Vin pin (although that is not supposed to be an output pin, of course).

Through thorough experimentation I've proven that both methods work.  

The best part is that the Uno can easily tolerate having both CCTV-style power and also being plugged into the laptop for programming and testing (like using the serial monitor).

Lesson learned:  The HC-12 simply will not work without auxiliary power, and it is safe to provide such power while also plugging the serial port into a laptop.