How Do I Add A Background Image for the form to lay on?

I'm trying to add a background to a form. I need bits of advice first.

1.) Where would I make the edit to place the image as a background?

2.) is the css as follows:

.gform_wrapper {background-image: http://mysite.com/folder/image.png;}

Please let me know if I'm in the right direction with my css and in what file I would place this bit of code.

I found the code in another post on the forum that had to do with changing the background color, however, I need to know where that line of code goes, as well as whether or not I have the css code written correctly.

Thanks in advance. I appreciate it.

Thanks Kev.....us Kev's gotta stick together!

Hi,
I think I'm trying to do the opposite -- I need to REMOVE the background image (bullet points) from my form, but am stumbling over the CSS. (I think I'm close but just a little off!)

I was told by my Wordpress theme designer to remove the background in a fashion such as this:

#some_id_from_the_gravity_form ul li {
    background: none!important;
}

so I have tried many variations trying to figure out which id layer #some_id_from_the_gravity_form refers to and came up with this:

#gform_wrapper_1 ul li {
    background: none!important;
}

It's still not getting rid of the bullet points so there must be something I'm doing wrong! Can you please help me out? Thanks!

Oh and I would post the link to my form, but the site isn't live yet and you won't be able to view it until it launches.