If the customers information is being saved but is not showing up in the admin panel, then there are two possible causes. One is that step 5 where you run the $setup->addAttribute() method didn't work correctly. The other problem could be that you did run this code, and it worked, but the attribute wasn't made visible. In this case you can safely run the code again but specify 'visible' => true as one of the array parameters.
If the customers information is being saved but is not showing up in the admin panel, then there are two possible causes. One is that step 5 where you run the $setup->addAttribute() method didn't work correctly. The other problem could be that you did run this code, and it worked, but the attribute wasn't made visible. In this case you can safely run the code again but specify 'visible' => true as one of the array parameters.