Help with iCLoud

i am just setting things up on my iphone and computer to use iCloud..... i think i set it all up, i even have an iCloud mail address...langloismaddy@icloud.com....

so i look up how to set it up on "This iPhone cannot be backed up because there is not enough storage available." But when i look at the storage it says....Total storage is 5.0GB and Available is 5.0GB... so to me that tells me i havents used any of my storage.... what is going on and what can i do to fix it...please and thank you for your help.