The short answer is, you cannot. I find it weird why Google did not include this option. The Nexus 7 home screen by default is set to 5 and I really have no need for so many screens.
Considering there are folders to help manage your apps, this option should never have been excluded unless Google did this on purpose to force users to spread out all app icons on the home screen then that would make folders have no use at all.
So anyway, if you really want to remove the other home screens, the only solution is to download some other launcher like Apex or Nova.
There are free versions of them and you can already manage the home screens with it. There is no need to purchase the pro or paid version in order to be able to manage home screens.
Man! This has really gotten me pissed! When Jellybean came out with the announcement that it will support higher resolution images (720×720) compared to what Ice Cream Sandwich did (2562×256), I was really excited.
But even when I sync my Android smartphone with Google Contacts, the contact photos still revert back to 96×96 versions.
I wondered why it took them very long to do something about this and I found out that it had been a few years back when this issue was raised. More than 3 years have passed and the GMail team still had not done anything.
So maybe they are doing something about it … but … 3 years have passed and not even a 256×256 support has not been incorporated.
This is actually the only feature I am looking forward if I were to upgrade my Android OS to Jellybean. I just want to see my contacts’ photos in high resolution.