You must be running iOS 5 on the iPad in order to use iCloud so you would have to update the device first. If you decide to update the iPad ....
What you should do anytime that you update the device is to transfer purchases from the iPad into iTunes - File>Transfer Purchases - and you should backup the iPad as well. When you update the update the device, if something goes wrong, you can restore from the backup.
However, iTunes should ask if you want to backup before you update, but just in case create the backup yourself before you update. The backup contains your app data and settings - along with other items - so make sure you backup first.
If you have any other important files, you may want to transfer them to your computer as well, prior to the update.
How to backup and restore from a backup
Here are the instructions for updating the iPad.
iCloud: Backup and restore overview
Check iCloud storage & backup space on iPad
iCloud: Troubleshooting creating backups
iOS 5: Updating your device to iOS 5 or Later
If you are currently running an iOS lower than 5.0, connect to your computer & click on the "Update your device using iTunes".
Tip - You may need to disable your firewall and anitvirus software temporarily. Then download and install the iOS update. Be sure and backup your iPad before the iOS update. After you update to iOS 6.x, the next update can be installed via wifi (i.e., not connected to your computer).
There's good information in the previous posts. I'll only add that since you have an iPad 2 you will only be able to upgrade the iOS to version 6.0.1.
Io5 did have iCloud capabilities but the iOS has continued to evolve and is now at iOS 6.0.1. Apple does not presently allow users to update to anything other than the most recent version their device will support.
I will also add that I too have an iPad 2 and it presently has iOS 6.0.1. It works very well with iCloud, my iPhone 5 and the MacBook Pro that I sync both devices with.