Insert meteor-slides like a code on frontpage

Hi,

I need some help, i have install the meteor slide plugin on my theme newswire, that have 2 widgets sidebar left+right.
If i take the widget and put it in one of the side bar become automaticaly small (150×150 i think), i need it like 300×250.
I try to modify de sidebar.php and page-sidebar.php and add this :
“<div class=”ad300x250”>ad code</div>”

Where it’s writed ad code i try different ways but nothing until now to solve .
thank you !