Here's what Apple says:
Because of how Find My Mac works, you must deselect the box next to Find My Mac in the OS X System Preferences > iCloud pane to remove your device from your iCloud Find My iPhone, iPad, iPod Touch, or Mac device list.
One of the ways this persistence is implemented is by writing a Find My Mac token to NVRAM, the persistent memory in Intel Macs. You can see this token by running the following command in a terminal:
nvram -p | grep fmm
On my Mac, the result includes my name, Apple ID, and the name I gave the computer, along with some encoded information that probably includes a key of some sort.
Unfortunately, you are very limited in what you can do with that backup. In fact, there is literally nothing you can do with an iCloud backup unless you restore the backup. This can be done, however, on any iOS device (as in iPhone, iPod, or iPad), that is at least the iOS version that the stolen device was on. For example, if the iPhone 4 was running iOS 6, you will only be able to restore to a iOS 6, or 6.1 device.
If you are on a Mac, you should have easy access to Calendars, Contacts, Notes, Reminders, and such data. If you are on a PC, you can access most of that by going to iCloud.com. This isn't really the data that you've backed up, though, and it's really data that is just "synced" through iCloud. Either way, Contacts, are typically pretty important.
If you own a Mac, you should be able to get your Photostream pictures by installing and opening Photostream. This doesn't capture videos, though.
If you do have an eligible iOS device that you can do a restore on, be sure to back up that device locally before wiping. It might also be advisable to make sure that device doesn't do a backup of the newly erased setup to iCloud. If you keep that iCloud account disabled on that device, you should have an easy restore from iCloud, and a backup in iTunes should something go wrong.
Best Answer
Unfortunately you cannot do this. Apple provides steps to Set up Find My iPhone on all of your devices, all of which require physical access to the device.
Since the notification email you received should have included an IP address, you could always try remoting into your MacBook Pro using Back To My Mac, Apple Remote Desktop, or some alternate method; and enabling Find My Mac that way.
However let’s face it: your chance of success here is extremely slim, and requires that you have allowed some kind of remote access to your MacBook prior to having it stolen.
Since the thief now has access to your iCloud account, your next step should be to head to id.apple.com and change your password immediately—before they do it for you.