There’s no real information or context here, it would be difficult for anyone to help you based on those details.
What API are you using? Is it public and are there any docs? What does a good request look like? How do you know what you have entered is correct for that endpoint?
Could you edit your question to include more information, please?
From that image, you can see that it’s not valid JSON in the request body. There’s an underlined red error indicator, which looks like it’s missing a closing " or its a multi line value that isn’t correctly formatted.
I don’t know what a valid payload is for that endpoint though so it’s just back to being guess work due to the lack of information.