I want to place some fields in the Security tab under Members before the Search and Member List section. They get added the the Group table and then appear after the Member List section. Here is my code so far:

class GroupDecorator extends DataObjectDecorator
{
function extraStatics()
{
return array('db' => array(
'Email' => 'Varchar(255)',
'Website' => 'Varchar(255)'));
}
public function updateCMSFields(Fieldset & $fields)
{

$fields->addFieldToTab('Root.Members', new TextField('Email', 'Email'));
$fields->addFieldToTab('Root.Members', new TextField('Website', 'Website'));
return $fields;
}
}

You can use the insertBefore() function rather than push to insert before a given field name (http://api.silverstripe.org/2.4/forms/fields-structural/FieldSet.html#methodinsertBefore) which is useful for inserting new tabs. For fields you can use the addFieldsToTab() with the optional 3 argument filled out with the field you want it to sit before (http://api.silverstripe.org/2.4/forms/fields-structural/FieldSet.html#methodaddFieldToTab)

Thanks for your response.
I did see those parameters for addFieldsToTab() but in this case I don't see what field I'm putting it before. For the default layout of the Groups/Members page there is a search and then a members list. I want to put the new fields before this and after the Title (Group name)

I took a guess and this works:
$fields->addFieldToTab('Root.Members', new TextField('Email', 'Email'), 'Members');
$fields->addFieldToTab('Root.Members', new TextField('Website', 'Website'), 'Members');

My new fields of 'email' and 'website' now appear before the members search and list section.