You can respond to a chargeback from two places inside of Disputes: My Work Queue or the Case Details Page.
From My Work Queue:
Find the table row that contains the case you want to respond to.
On the far right side of the row, click the “Actions” dropdown.
From the dropdown options, choose “Accept” or “Challenge”.
You will be taken to the first step of responding to the chargeback. Follow the prompts until you reach the final submission step.
From the Case Details Page:
Click the “Take Action” button in the top right of the screen.
Choose either “Accept” or “Challenge”
A panel will open at the top of the page with your next steps.