Once you have been through the process of selecting who to send your message to and composing the message you will then be able to add attachments to the email you are sending out.
Please note you can only add an attachment to the email message, not to push notifications or SMS mesages.
Select the Choose File button
Select your file from your computer
You can see that your file has been added, the name will appear next to the Choose File button.
Once you are ready, select next to take you to the Send screen.