Ghost on AWS - how to customise my blog and change the instance url to my domain

I have just installed Ghost on Amazon Free tier following the recommended page.

I can see my personal instance of Ghost live no problem, by pasting the public DNS into a browser.

How do I customise the blog? Do I have to install a SSH client?

My personal website lives on a different host (GoDaddy).

So how do I change the current AWS instance url to a subdomain of my website?

I have looked at this page but it seems quite painful. Is there any other route?