Add text boxes in columns help

I have used the plugin Column Shortcodes to create 3 columns and added some short text in each column, just underneath the header and menu bar on one of my pages.
Problem:Looking at my page I now feel the page would look better if I had a thin square box drawn around each block of text. I have searched for hours and tried a few things but just cant get this happening.
Is there an expert out there that can help with this frustrating simple problem?
I don’t know coding so any good help will be greatly appreciated.

Thanks

Franck