Once on the attachment window, click Browse to find the file you want to send.
Use the drop down arrow to find the folder the file is saved in
When you find the file, click on the file and it will appear in the File name box, then click Open
The file will now be selected
Click Attach (circled in Green above) and the file will attach to your email by moving to the white box as seen below.
To Get back to your Mail message, Click the Mail Tab (circled in blue above).