Transparency

I have reviewed the other support topics on this but I am getting hung up with finding "Additional..." To put in the CSS code you shared. I have a photo on the background, but I want my content, to not have the white page background. My url is https://pinkladyrochelle.wordpress.com/ If you can help, please let me know. I thought I could do it, but I am just not seeing the "Additional custom ..." Please forgive me, but I cannot even remember what you called it. thanks