Your account settings at WordPress.com can be accessed from WordPress.com by going to your Gravatar image in the upper right and clicking Settings in the drop-down menu. You can also click on your name and Gravatar in the admin bar on any WordPress.com site.
Username: This is your current username. You can change your username by clicking the “Change” link next to it.
Email Address: Required. You may change this, but note that email addresses cannot be shared among accounts. That is, one email address cannot be registered with multiple accounts. You will need to confirm by email when changing your email address.
Although your email address will not be displayed publicly on WordPress.com, when you submit a comment while logged into your account, the e-mail address will be transmitted to the blog’s owner/administrator.
Primary Blog: You can choose which blog you want to be your primary blog here. If you only have one blog there will be no dropdown.
Web Address: Not required. This is the URL that will be linked to your username when leaving comments on WordPress.com blogs. Please note that this is stored at the time of the comment, so if you do update this, it will not affect past comments (only those made in the future).
Fun: It wouldn’t be any fun if we told you what this does. Just try it out for yourself and see what happens.
Instant Post Feedback: Uncheck this option if you no longer want to see the instant post feedback after you publish new posts. For more information on instant post feedback please see this blog post.