Help creating minimalistic section & site border lines

Hi Squarespace community,

I am trying to figure out how to create a thin line border around my website and around specific sections (like in this example website: https://contrabass-grape-cmtm.squarespace.com/) 

I am new to web design, so I am wondering if there's a way to add a CSS code to achieve this custom border look? I have been trying to find a tutorial but haven't found anything!

Thank you in advance! 

With this, they used Line Block

With vertical line, they used Markdown with HTML/CSS code

You can share link to your site, we can help you achieve similar border easier

Okay thank you! The link to my website is here: rebekahvijaymedia.com

I was wondering how to apply the line block to the top and bottom of certain sections as well.  For example I have scrolling text below the header of my landing page, and I have a line block above it but I'd like a line below it as a border as well.  How would I achieve that? 

Thank you!