Q: mail drop. How do I retrieve from mail drop?

There should be a link in the email to the MailDrop video. Just click it.

iCloud: Add an attachment to an email

http://appleinsider.com/articles/14/10/17/how-to-use-mail-drop-and-markup-to-sen d-large-emails-in-os-x-yosemite

Kenstot,

The recipient of the email should be able to download the attachment.

Mail Drop limits - Apple Support describes some other considerations.

iCloud: Add an attachment to an email details additional information.