You have to follow this answer, then you replace the install script with this one:
<?php
$this->addAttribute('customer', 'license_number', array(
'type' => 'int',
'label' => 'License Number',
'input' => 'select',
'position' => 120,
'required' => false,//or true
'is_system' => 0,
'source' => 'eav/entity_attribute_source_table',
'option' => [
'values'=> [
0 => 'Information 1',
1 => 'Information 2',
2 => 'Information 3',
]
],
));
$attribute = Mage::getSingleton('eav/config')->getAttribute('customer', 'license_number');
$attribute->setData('used_in_forms', array(
'adminhtml_customer',
'checkout_register',
'customer_account_create',
'customer_account_edit',
));
$attribute->setData('is_user_defined', 0);
$attribute->save();
Nb: The attribute wil be stored in eav_attribute table.