Step 1: Download the xml file from my site and save it on your computer.
Step 2: You should always backup your current template before installing a new one. To do so, go to your Template page and click Backup/Restore on the right side of the screen. Click Download Full Template and Save. Find a folder on your computer to save it to.
Step 3: Go to your Template page and click Backup/Restore on the right side of the screen. Select the second option under "Upload a template from a file on your hard drive." Click "Choose a file" and select the xml file you've downloaded from my site and click Upload.
You're done! :]