Well, welcome to the forum! BUT, you provide basically no information to help us even respond to your terse question - quite frustrating!
First, what iCloud account do you have? The 'free' offering provides just 5 GBs of storage and you're trying to backup two iDevices. Second, how much free space is left on your iPhone & iPad - the difference (depending on your storage originally) will give you some idea of what needs to be backed up to the cloud (of course, this will vary depending on the types of data on your iDevices).
So, help us first - what account do you now have on iCloud and 'how much' data do you need to back up? You likely just do not have the cloud space w/o paying more - Dave