Edit css of Affiliate page

I am curious as to how I can edit the CSS file for the Affiliates page on the front end of my website. Take a look at my website:
Affiliate page link

Id like to make the following changes to the css:

• Change background from white to transparent if possible. If not, then black #000000
• Change text from gray to white #FFFFFF
• If possible increase the dimensions of background or something so that the text doesn't exceed the background

The CSS can be edited in the Display tab of the configuration.

The CSS:
#hikashop_order_listing fieldset, #hikashop_address_listing fieldset, #hikashop_affiliate_main fieldset {
border: 1px solid #CCC;
background-color: white;
}

set the background to white so you can change that to another color or transparent if you want.

There, You will be able to add the color attribute and add some padding to avoid the text going over the top.