To change the wordpress theme on your blog follow these easy steps:

1. Extract the theme from the archive (zip/rar/whatever)

2. Upload the theme files on your ftp server in /wp-content/themes/

2. Authenticate yourself and go to your wordpress administration panel

3. Click Design and a page will load with the themes found in your /wp-content/themes/ folder

4. Click on the theme you want to activate it.

5. Customize the sidebar(s) of your theme by editing the Widgets.

Have fun!