You may want to attach a file to a message that you have created.
To add an attachment to a message:
One of the new features in Outlook 2013 is the Attachment Reminder feature. Outlook 2013 can detect if you intend to attach a document and, if you do not, it will alert you.
In the following email, you will notice an attachment is mentioned, and then Send was selected; however, no attachment was added to the message.