To delete respondents from a panel, go into panels in the top bar and select the specific panel you want to look at. Here, there will be a summary page of all your panel respondents. You want to click the 'Individuals' button above it, which will bring you to a page that looks something like this:
From here, you can scroll down the page, and click the grey delete button next to the edit button. Remember to click this button and not the red delete button at the bottom of the page, as this will only delete the specific response, rather than deleting the respondent entirely. The button you need to click is circled in green in the image below.
If you want to delete all the respondents for a panel, go to the 'Settings' button on the sidebar within your specific panel, and then click the 'Delete all subscribers' button at the bottom of the page.
If you have any questions about this or anything else, please don't hesitate to contact us at firstname.lastname@example.org.