how do delete photos on my iPhone without deleting them on my computer
How do I delete photos from my iPhone with deleting them off my mac
and iPad
iPhone 6s, iOS 9.1
If you have iCloud Photo Library turned on in all of those devices, note that any photo that you delete from anywhere (iPhone, Mac, iPad, or iCloud) will be deleted from all of those locations. You can reduce the space required on the phone by turning on Settings > iCloud > Photos > Optimize iPhone Storage.
If you want photos to transfer from your other devices and to then be able to delete them from your phone, you may want to investigate using Photo Stream on your phone instead of iCloud Photo Library. In that case, be sure that you understand how to automatically import items from Photo Stream into your photos library in iPhoto or Photos. See My Photo Stream FAQ - Apple Support for more details.