Microsoft have recently updated their Office 365 email software, with a greater emphasis on the use of their cloud based OneDrive folder.  The below is the updated method to attaching a document from your My Documents folder, or other location on the network.

Step 1
Create your new email, or reply to an existing email as normal.

Step 2
From the INSERT menu, choose ATTACHMENTS OR ONEDRIVE FILES.

Step 3
The default location to insert a document from has now been changed to OneDrive, but to add a document from your My Documents or other Network location click on the COMPUTER icon and the normal browse window will open.  From here you can browse to whatever location and files as normal.

Step 4
Because Microsoft really want you to start using OneDrive, you’ll be asked if you want to UPLOAD AND SHARE WITH ONEDRIVE or SEND AS ATTACHMENT.  To attach a file as normal, simply select the latter.

The UPLOAD AND SHARE WITH ONEDRIVE option is a very useful tool to use, but may require some training to get the most from it.  For now, you can ignore it.