New iphone owner needs help

If I want to save my photos on my PC do I have to move them from the Photo Stream File on my PC to another file on my PC?

How do I save photos on my iphone from the photo stream to the camera roll as they seemed to have been deleted when I manually download them onto my PC?

My iphone says I don't have enough storage to back it up yet the storage says I have 3.58 GB left of 5GB?