how to add license to ESXi 5.1

Hi every one

I have just installed ESXi 5.1 hypervisor and am trying to add the license key. When I try to creat a virtual machine it tells me this version of my esxi is trial and will expire in 60 days. I searched for how to add the license key and all I found is to go to "home" and then "administration" but when I click the home in the menue up there, and choose the administration from the menue in the menue bar, it only shows me "role" option and there is no other option.

I would appreciate it if anyone can instruct me how to add license key to the product.

regards