How to add a background image on specific webpage instead of all pages

Hi,

I an using t3-blank template,I have tried extension modules like bgMAX, HD-Background Selector, etc to solve background image on specific page, but it doesn't work, I don't know why????

So, how can I set the CSS code on specific page (the whole page including header, body) so that a background image only shown on specific page.

Or others alternative solution, thanks in advance.


Patrick