I am absolutely rubbish with stuff like this, and usually get my DH to do it, but he's not here so I would love some help :)
My iPhone is full, can't take anymore pictures etc, and gave me a 'manage storage?' option which took me somewhere in settings that said my phone was full but my iCloud empty.
I also have an iPad so thought that through wifi or something all photos etc transferred to both devices?
Does that even make sense!