Hello,
I'd like to know how to add a border around the entire body: posting and header.
Thank you.

Just add a border to ATO>Style & configure Layout>Layout Container Style

At some point, I removed the space above my header. See: www.embodiedawake.com.

I'd like to add some of it back again. Can you remind me how I did that? Will I be adjusting margins or padding? I'm still confused about them.

It's top margin on #container or top padding on #wrapper. You might have to add !important.

Where would I find this? I've feel like I've gone through the whole menu of options but am still overlooking it.

It's not a matter of finding it. It's adding it to ATO>Add HTML/CSS Inserts>CSS Inserts such as

#wrapper {
padding-top: 20px !important;
}