1) Make a backup of your site using the backup icon > "Generate New Fresh Backup" from your members cpanel.
2) "Make the Backup file available for download" and then Download the backup file just created.
3) Click the "website builder" icon from members cpanel main menu
4) Click the link provided in step one of the onscreen instructions, and it will open a new window or tab with the sitebuilder.
5) Change the URL in your web browser as follows:
Note: Yours will be slightly different as it will have yourwebsite, username and password instead of the example ones below
Make sure you leave EVERYTHING before and after sitebuilder.php exactly the same and just change sitebuilder.php to upgrade.php as above.
6) Make sure you Hit enter or Go from your web browser so it loads the new URL.
7) Click on "Next Step->2" button and after a long wait
, you should get a screen with some "Upgrade Options".
8) Tick the box which says "Template (Graphic Design)"
and untick all other boxes
9) Select the template you want to add from the left hand side list. It will appear in the preview pane also.
10) Once you have selected your template, click "Next Step ->3"
11) Enter the details requested (Company/Website Name; Slogan; Keyword META Tags; Description META Tag)
12) Click "Go ->Install my website"
13) You should see a congratulations message (but we're not finished yet!!)
14) Go to the admin link listed on the congratulations page and log in to your admin page. The user name and password should be the same as you had it before.
15) Click on the "Config" tab from the toolbar
16) Find the "Default Template" dropdown to change your default template (you will have the original one and the new one listed).
All of your old content should be intact, however, if it isn't you can restore the backup you made in step one, and as long as you don't delete the old files, the new template should be there as well.
This should also allow you to add other templates, and if you know how to use the website builder well, then you can also have different templates between different pages too. Of course, you can also create your own templates, which can be even more rewarding than using someone elses!
Hope that helps (and if it did, feel free to click Karma)