New to WP and lost…help?

Hi there I am helping a friend who knows nothing about computers, but now looking at WP i feel I don’t know myself ??

Well at first i thought it was going to be like Blogger where you can create an account, add or remove elements for your page and be able to have access to post your thoughts.

I don’t know where to begin, I have a theme she purchased and I just have to tweak it to add her logo and change colors and add the members sign in option, but I don’t know where to begin.

I downloaded the WP 2.7.1 thinking it will be an application to upload my theme and work from there….buts it a folder with files.

So should I be using Dreamweaver to upload this theme and make the changes on Dreamweaver or is there another way?

She has a domain name and hosting with GoDaddy, but where do we go from there?

Hope someone can help

Thanks