Thomaz,
Your first HTML record probably saved the data in a database, right?
When you view the second change page, you should:
Get the previously registered database data (with PDO, mysqli_ * functions or some ORM)
Place these values in your HTML form, for example:
<input type="text" name="nome_usuario" value="<?=$usuario['nome']?>" />
And perform the change action of the new one on the new form.
If you want to use the same HTML form both on the registration page and on the editing page you need to take care of three things:
Change the form's action if it is editing or registering:
<form action=""<?=$urlCadastrarOuAlterar?>"
In the values of the fields, you will have to check if there is a user:
<input type="text" name="nome_usuario" value="<?=isset($usuario) ? $usuario['nome'] : ''?>" />
In the case of editing, save the user id in a hidden field.