Is it possible (and how) to add content, namely phone number and perhaps address at the top right corner? I have limited HTML/CSS knowledge

Thanks in advance!

You can put code in the HTML Inserts: Body Top box and position with CSS. For example
The html might be

<div id="top-address">Type address here</div>

and the CSS might be

#top-address {text-align:right;}

These are just examples. To find out more about CSS go to w3schools.com

Thanks for the reply Imilesw

Are there any instructions that's more specific to making the edit within Atahualpa?

I have crawled through all the Atahualpa options, do you think "Widget areas" would help?

just add it to the ato->Style & edit HEADER AREA->Configure Header Area

Thanks for replying juggledad but unfortunately that just adds either below or above the logo. What I would like to do is add the phone number to the top right corner and within the border.

http://www.acupunctureclinichouston.com/

I currently just use a wide logo image but the header should show where I'm talking about. Thanks

So you would use something like the following in the same spot Juggledad mentioned.

<div style="text-align: right;">315.555.1212</div>

CSS is VERY important to learn for website building.