help customizing the extension

lets go to my problem:
I'm using "HOT Joomla Gallery" in various articles on my website. Sometimes I use it in total pixel size in the site but sometimes I want to use it in a smaller size. When I do it, the thing i put in my site, it´s been aligned on left. I want put a thing centralized, but if i change to centralized, all the articles into the site stayed centralized. Ive tried to do on the css extension but it cannot do it because when i fixed the small, the big stay centralized and incorrect.

I need to know how can i do for configure to use custom when i want to use small without change biggest.

What is your site link?

www.euqueroforever.com.br/web

Add this to template_css.css:

#hot-joomla-gallery-wrapper > DIV{
margin:0 auto;
}