How to get the ios 7 on iphone 4?

I've been notified that ios 7 works on the iphone 4. How can i go about getting it updated on my device?

Settings> general> software update. It may take a while because people are hitting the apple server hard today ( they are all using it to dowload the ios 7 update) :-)
Enjoy the update.

Just go to your settings, general, software update and it will say that there are no updates but wait a minute and hit download&install and agree to the terms and keep your phone plugged in cause it does drain your battery a bit more and it should take less than an hour, Enjoy!

I agree with the other answers but they haven't mentioned to plug in your phone to a computer which i highly recommend so you don't lose any of your stuff when it's updating. Also many people are reporting bugs and glitches because iOS7 was mainly focused around the new iPhone 5c and 5s so i would wait a bit to get it. Maybe a week when they will come out with iOS 7.0.1 that will have solved the glitches.