There are three ways to change directions. The first one is to go through Easel Set up where it asks you to try the movements and asks if they are in the correct direction. The other is to go into the GRBL settings and manually change them. It is $3= one of the numbers from the chart. You would enter one of the numbers 0-7 depending on which axis or axes needs to reverse direction. The last is to change the wires in your connectors.
GRBL_Settings_Pocket_Guide_Rev_B.pdf (diymachining.com)
To view your settings you type $$ in the command line. To change a setting you type $= (pick one of the numbers 0-7 )and hit enter.
X-Carve Instructions: Computer Setup (inventables.com)
Y1 axis moves opposite direction from Y2 - X-Carve - Inventables Community Forum