How to restore UEFI boot?

Hi!

One year ago, I deleted the uefi settings on my laptop, to install Win 7 and I set Legacy mode.

Today, I want to install Win 8 and enable Uefi Mode, but "UEFI BOOT" menu is empty. I can't add new boot option because it's ask me only the name :S

How can I restore UEFI mode or add new boot option?

My laptop is an Inspiron 15R 5520