Sorry.
Please let me be more detailed - given TM hasn't changed too much, and left the comments on the file.
Browse to includes/templates/TM_TEMPLATE/templates folder, in there you could/should have a file named tpl_product_info_display.php open it in a text editor like notepad++ (if you don't have it google for it), here you should see something like <!--bof Add to Cart Box --> before that you could add a
<div id="myAddAttributeBox">,
then you should have something like <!--eof Attributes Module --> after that you add
</div>.
After this you browse to includes/templates/TM_TEMPLATE/css folder, and open the stylesheet.css file in the editor, and add at the end of it
Code:
#myAddAttributeBox {
border: 1px solid #FF0000;
}
Now you upload the two files in the respective folders to your server.
You might need to tweak a little bit with the other rules to get it display like you need.
NOTE
In case you have hard time locating the tpl_product_info_display.php file, use the
admin > tools > developer tool kit
to search for either <!--bof Add to Cart Box -->, or <!--eof Attributes Module --> to locate it.