How to use iCloud on iPhone 4s?

I have restored my iPhone 4S by plugging it into my iTunes and lost everything, I managed to sync my songs & apps but have lost my contacts and photos:/ I remember setting up an iCloud when I first got my iPhone which I've been told backs up everything you have on the phone? So what I want to know is if iCloud has backed everything on my phone- how do I reverse it & get it back on my phone?

ICloud would have only backed up your iPhone if you turned it on in the iCloud settings. Your only way to check is to restore your iPhone and then when you turn your phone on, try to restore from iCloud backup.