<p>You can read the information on Meta Stack Overflow under "<a href="http://meta.stackexchange.com/questions/793/how-do-i-change-my-openid-providers">How do I change my OpenID</a>":</p>

<blockquote>
  <p>This is documented on the <a href="http://blog.stackoverflow.com/2009/01/we-now-support-multiple-openids/" rel="nofollow">Stack
  Overflow
  blog</a>.</p>
  
  <p>Go to your user page and click <strong>add
  openid</strong> or <strong>change openid</strong>.</p>
  
  <p><img src="http://blog.stackoverflow.com/wp-content/uploads/openid-multiple-association-2-new.png"></p>
  
  <p>Note that once both are populated, the
  <strong>primary</strong> OpenId will be overwritten if you associate another OpenID.</p>
  
  <p>You can use the [swap] link (not
  pictured) to switch your primary and
  secondary OpenID at will.</p>
  
  <p>After changing, <s>beware that copying
  your profile to other accounts <a href="http://meta.stackexchange.com/questions/5656/copy-profile-from-stack-overflow-didnt-copy-alternate-openid/6018#6018">does
  not copy the OpenID
  details</a>.</s> you might want to click on "Copy Stack
  Overflow login credentials to all
  Stack Exchange sites"</p>
  
  <p><img src="https://i.sstatic.net/hrILU.png" alt=""></p>
</blockquote>