Colored Vertical Borders

I am a little confused about adding vertical borders. I have looked through the Themes and Co FAQ and have had no luck. Is it possible to add a border that starts at the far right and goes almost the the edge of where the content starts on both he left side and right side of the screen? Also while I am here, I was wondering why there is a white area on the far right of my website. is there something wrong with the CSS I have put in? My website is https://www.cookiedoughtreats.com.
Thanks!