When I go left it goes right and vice versa

Just finished my build on SO 3 and it worked! Only thing it goes right (X) when I toggle left and same thing when I press left it goes right. Somewhere I read it said to reverse the GRBL, not sure what that is and how to do it.
Please help…

Open up Carbide Motion Machine Control Software.

Hit L to show the Log window
Hit M to bring up the MDI window
Send $ to get the current machine settings

Based on the setting of the $3 variable you’ll want to add or subtract 1 from it. See http://www.shapeoko.com/wiki/index.php/Grbl#Grbl0.9

eddieb, I’d suggest checking the colors of the X axis stepper motor wires at the plug. A common reason a stepper motor runs in the opposite direction as expected, is that two of the wires are swapped. Looking at the Shapeoko assembly PDF, the X and Z motors are interchangeable, so their wiring should be the same at the plug. You didn’t mention the Z being reversed, so if it is working the expected direction its wiring is correct.

(oops, I see WillAdams replied while I was typing. My post is more in the vein of “why is it behaving as it does” and looking for a root cause. Will’s advice will fix the issue in software without needing to know the cause)