Delete photo from iPhone 5c without deleting them from photostream?

I want to free up space on my iPhone 5c, so want to delete photos from my iPhone without deleting them from photostream. Ideally, I'd like to be able to do this anywhere (i.e. without having to be by a computer).

I'd also like a way of knowing which photos are being stored in the cloud and which are being stored on my phone, because at present the photos app on my phone is showing all the photos I have on iPhoto on my computer. How do I delete photos being stored on my phone without deleting them from iPhoto on my computer?

Thanks