By Asura.Daleterrence 2010-06-26 12:29:14
Drop down Menu over to the right of this post, and select "Edit Account", its half way down the page for this website.
If you mean your POL one, you'll have to login to PlayOnline, go to the POL top page, click "Service and Support", then click Membership, then on the menu at the bottom of the screen that appears, click "Update PlayOnline Password".
Edit: Beat to it. Also, put more context into your OP lol.