Follow the steps given below to approve/reject a request:
You can also see the pending requests under notifications, since a notification is created for all the admins whenever there is a new request.
You can also approve the request from the link that is provided in the notification mail that's been sent to all the admins while creating the request.
Only Admins can approve/reject a request.
Note: In case of few requests like script execution request, you can approve the request and allow the scripts to run immediately or you can choose to schedule the script execution. This option is not available for all the request types.