* Click 'Create new users' and create a user for Perkeep (keep 'Generate an access key' checked)
* Click 'Show User Security Credentials' to get the users Access key and Secret key - these will be required to configure Perkeep and can't be obtained after you leave this screen.
* Go back to the user list and select the new user, and on the 'permissions' tab add the following 'inline policy' (replacing YOUR_BUCKET_NAME with the name of the bucket you created)