While your journal will contain the bulk of information about your account, there is also a User Info feature available. Your User Info is available at http://www.insanejournal.com/userinfo.bml and can be modified here, where you can also edit your journal preferences.
Updating your journal is also an important part of using the site. To post an entry, click on the "Journal" drop-down menu and select "Post," using the default site scheme. This will take you to the Update Journal page. You can also update your journal with the Portal.