For attachments, you can add new attachments to the template as many as you would want to send. Each attachment has a type, file data key and a file name key. The file data key and file name key would be like {{attachment_1}} and {{attachment_name_1}}. The type specifies whether the attachment is a text file or some other format (PDF, JPEG etc). The attachment data should be encoded in Base64 encoding and passed as a value to the file data key in the Send Event API. Also, the name of the attachment that you want to send in the email should be passed as a value to the file name key.