If you have new information and want to add to an existing story, you can always do so.
First, log in with your email address and password. To do this, go to the homepage and click the "Log in/register" icon in the top right corner of the screen.
Then go directly to the personal page of the person you want to tell more about. There, you can view and edit your story. Go to the story and click the blue "Read more" button at the bottom. You will now see the text with the "Edit" button below the story title. Click this to edit your story. Don't forget to save the story.
You can also edit your stories via My Account. There you will see your latest contributions. Now hover your mouse over the box of the contribution you want to edit. A blue "Edit" button will automatically appear below the story title.