You cannot open the file 1st of all.
2nd, there should be an additional folder labeled "custom tunes" (on the SD Card).
You'll want to place your downloaded file into that folder.
To do that, right click on the file (from the email LMS sent you)
Click on "Save As" and save it to your desktop.
Insert the SD Card into your laptop/notebook.
From the Desktop, right click on the downloaded file and then select "Send To"
From there, send it to the SD Card.
Open up the SD Card folder and then left click on the tune file you just sent and move it into the "Custom Files" folder.
Wallah. Done. Eject the SD Card from your notebook/laptop.
Make note of the file name, as when you reinstall the SD Card into the MyCal device, upon selecting "load tune", the device will bring you to w/e custom files you have available to you (i.e. your new tune file) then select it & follow the prompts.
That should get you through.
If it doesn't, then place a call to LMS for a more thorough walk through.