Keyboard: update readme with ps2avr flashing instructions (qmk#4776)

keyboards/mehkee96/readme.md

@@ -12,5 +12,35 @@ Make example for this keyboard (after setting up your build environment):
 
     make mehkee96:default
 
-See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).
+Flashing
+
+ps2avr(GB) boards use an atmega32a microcontroller and a different bootloader. It is not flashable using the regular QMK methods. 
+
+Windows: 
+1. Download [HIDBootFlash](http://vusb.wikidot.com/project:hidbootflash).
+2. Place your keyboard into reset. 
+3. Press the `Find Device` button and ensure that your keyboard is found.
+4. Press the `Open .hex File` button and locate the `.hex` file you created.
+5. Press the `Flash Device` button and wait for the process to complete. 
+
+macOS:
+1. Install homebrew by typing the following:   
+    ```
+    /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+    ```
+2. Install `crosspack-avr`.  
+    ```
+    brew cask install crosspack-avr
+    ```
+3. Install the following packages:
+    ```
+    brew install python
+    brew install pyusb
+    brew install --HEAD`https://raw.githubusercontent.com/robertgzr/homebrew-tap/master/bootloadhid.rb
+    ```
 
+4. Place your keyboard into reset. 
+5. Flash the board by typing `bootloadHID -r` followed by the path to your `.hex` file. 
+
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).