How to transfer images from computer to iphone 5s DCIM?

Why can't i transfer images from computer to iphone 5s DCIM, i connect my iphone to my computer i open the iphone storage and i click the DCIM and i can drag the images from my computer but i can't transfer it. My iphone is unlocked but i can't transfer, all i can do is synchronize my iphone! I used to do this method but now i can't. I want all the images to camera roll

Because you can only put photos on your phone from a computer by syncing via itunes. You are out of luck.

Three easy ways to transfer photos from computer to iPhone,
The first way is to upload your photos from computer to iPhone via iCloud,
The second way is to transfer photos from computer to iPhone with iTunes
The third way is to transfer photos from computer to iPhone with MobileGo for iOS