Go to the Square App you have created from your Square Account. Select Sandbox from the top and then select Credentials from the left sidebar.
You will get a Sandbox Application ID and Sandbox Access Token.
Square Application ID and Access Token Sandbox Mode Square Payment
Now head on to your Magento store admin. Go to Stores > Configuration. Under the MageComp tab, select the Squareup tab. Expand the General Configuration option.
Application Mode – Select the Sandbox option for testing payments through Square.
Sandbox Application ID – Copy the Sandbox Application ID from the Square account and paste it here.
Sandbox Access Token – Copy the Sandbox Access Token from the Square account and paste it here.
Click on the Save Config button.
Now, expand the Oauth Configuration option.
Oauth Configuration Sandbox Mode
Get Sandbox Location – Click the Get OAuth Token button to retrieve the location.
Sandbox Location – Select the location from the dropdown.
Again hit the Save Config button to apply your configuration settings.
