The Share This Post feature will allow you to send links to your new posts to your Twitter and/or Facebook accounts by simply selecting the option from the Compose page. Sharing your content on social networking sites is an effective way of increasing traffic to your blog and gaining new readers.
If you are interested in the ShareThis social media sharing widget, it is a different feature, and you can configure the widget at ShareThis.
Setting up Your Accounts
In Account > Other Accounts, use the Add an account menu to select Twitter, Facebook or Facebook Page and click Add Account. In the pop-up window, enter your member name and password or key for the service. In order for Share this Post feature to work, you must provide the password or key for the account. You can enter multiple Twitter, Facebook, and Facebook Pages. For more information, see the sharing posts on Facebook and sharing posts on Twitter.
Using Share This Post
After configuring your accounts using the instructions above, you'll see an option on the Compose page to notify the services you've set up. Use the check boxes to select the services you'd like to update. When you publish your post, the services will be updated with a link to your new post.
If you would like the Share this Post feature to be on by default, you can select that option from Settings > Sharing. The default setting can be overridden on a per-post basis, using the check boxes on the Compose page.
Incorrect Log In Details
If you see a trouble icon on the Compose page next to a service, that means that either the member name or password/key that you've set for that service is incorrect. This may happen if you change your password at Facebook, for example. If this happens, go to Account > Other Accounts and use the Edit link to update the log in details.