How add placeholders to fields

Hello,

Please how can I convert the labels to placeholders, I want the labels hidden while using placeholders.

I don’t know if this example code could work

// Add placeholder to buddypress registration form.
function wp_add_placeholder($elements){
    $elements['placeholder'] = bp_get_the_profile_field_name();
    return $elements;
}
add_action('bp_xprofile_field_edit_html_elements','wp_add_placeholder');

Thanks