Making Main body of Swatch Theme transperant

Hey,

wondering if someone can help me out, I have downloaded the swatch theme, and I am trying to make the main body, where my posts coming up transparent, as currently it is hiding my background.

I have had a look at the style CSS but to my eyes anyway there is no /*Main Layout*/ section to edit..

Any tips what it may be under?

My site is https://captainslow.ie/ but i have the maintenance plugin active