How do i upgrade my new P8lite ALE-L21C185B160 with 5.0.1 to the latest?

It is currently running Android 5.0.1 and from what i can read it should be able to get Android 6.0. But if i go to About and search for updates, nothing is found.

I am using P8lite ALE-L21C185B160 with 5.0.1 in Pakistan.

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