How to back up my Iphone 5S to my ICloud?

I updated my Iphone to 8.01. It kept saying, 'This iphone hasn't been backed up for 5 weeks". I finally made a ton of space on my phone by deleting apps and now have the space to back up my phone. BUT were in the world is the button that I press that says, Back up to Icloud? I go on Settings then Icloud and then what? Please be simple with your explanation.

You want to go to settings and then scroll down to iCloud and select it, now with in iCloud scroll down until you see Storage and Backup and select it and now you will see the space you have on you iCloud,
and now you should have iCloud backup turn on and under that is a option back up now select it and your iPhone will do a backup