Not enough Storage This ipad cannot be backed up because there is not enough iCloud storage available. you can manage your storage in Settings. Que puedo hacer porque no puedo utilizarlo, esta bloqueado

I have an iPad 2 and when I want to use it I can`t do it because a message appears saying: "Not enough Storage" : This iPad cannot be backed up because there is not enough iCloud storageavailable. You can manage your storage in Settings.

What can I do because it is blocked and I can`t use it? please I`ll be waiting for your comments.

Thanks a lot.

Estefip