iOS8 has arrived for your iPhone and iPad and the following will help you make the move. Remember to back up to your computer through iTunes or make sure you are backed up through iCloud and that you have enough space on your device (5.78gb ) to do the upgrade.
Here is a great article and post from CNET on making the upgrade to iOS8 for Apple devices.
Then here is advice about when to make the move to the new iCloud drive
Lastly a review of iOS8 from the Wall St Journal