Center section ‘subsribe’

Hi,

I would like to center the white block with text in the section Subscribe on my website.
my website

I already changed the width of the block, now I would like to center it.
What code could I use for this?
(it’s vital the text margins stay in place; I tried some code but this resulted to no margin between box-border and text left and right).

Thanks!

The page I need help with: [log in to see the link]