No "New vApp" option available

Hello,

I'm using ESXI 5.1 and accessing it with same version of vsphere, the problem is that when i right click on my ESXI host there's only 2 options

- New Virtual Machine

- New Resource Pool

But no "New vApp"

Anyone knows why something like that could happen? In case you are wondering were i found the missing option is in "The Official VCP5 Certification Guide",

I'm using the 60 period, could be something related with the licensing?

Thanks.