
Click the File down-down menu, navigate to Examples->Grbl, and select GrblUpload.zip file or the wrong folder, you will need to navigate to your Arduino library, delete the mistake, and re-do Step 3.
IMPORTANT: Select the Grbl folder inside the grbl-master folder, which only contains the source files and an example directory. Click the Sketch drop-down menu, navigate to Include Library and select Add. Load Grbl into the Arduino IDE as a Library. Make sure you are using the most recent version of the Arduino IDE!. Unzip the download and you'll have a folder called grbl-master. Click the Download ZIP button on the Grbl home page. On Windows, it's in My DocumentsArduinolibraries. Otherwise, you'll have compiling issues! On a Mac, Arduino libraries are located in ~/Documents/Arduino/libraries/. NOTE: Before starting, delete prior Grbl library installations from the Arduino IDE.