Access Requests are registered per BowerKit. Head to your BowerKit, click on the 'Manage Access' button, or 'Access Control' links. Here, you'll be able to respond to each request.
Alternatively, you can try our Beta Access Requests Dashboard here. This will show you all pending access requests across your BowerKits.
Here, you can provide different access levels to users (View, Low-Res Downloads, High-Res Downloads, and Edit Access). If you would like to reject an access request, please first send a message to the user letting them know why you're rejecting the request. You can then click the red X to remove the request.