Where to place adsense code?

Guys,

I need to place adsense ad into rectangle (please see the image below):





Here there is initial html code:

Where exactly should I insert adsense code in the initial html code above?
Thank you very much in advance for your help.

 

replace

<td style="background: url('images/bigred/gradients/gradient_banner.gif') repeat-x;"></td>

Code (markup):

to

<td>ADSENSE CODE</td>

Code (markup):