WordPress API key
1. Activate “Akismet”, in Plugins click “Akismet Configuration”, input WordPress API key, which you can get after registered wordpress.com, and received email from wordpress.com
More of WordPress API: http://wordpress.com/api-keys/
2. WordPress.com Stats
statistic chart of your WordPress website.
Download stat from: http://wordpress.org/extend/plugins/stats/
upload stat.php to your directory: /wp-content/plugins/
Activate stat
Enter API Key, and add your blog to WordPress.com
3. Popular Posts
“WordPress.com Popular Posts”
After installation of Stats(API Key & 2), you can make this plugin working now.
Download: http://wordpress.org/extend/plugins/wordpresscom-popular-posts/
unzip, and upload them, including sub-directory.
Activate
Design–>Widget–>add to sidebar