How do I remove photos from iPhone 5c?

If you are using iCloud Photo Library there is no option to delete photos from any device or iCloud without them being deleted from all of the devices which are using iCloud Library and from iCloud. The most you can do to reduce storage required on the phone is to go to Settings > Photos & Camera and turn Optimize iPhone Storage to on.

You could make a suggestion for that option to be offered: https://www.apple.com/feedback/icloud.html

It is hard to answer without more details, but here is some information:

As I said before, if you have iCloud Photo Library turned on then any photos you delete from the phone will also be deleted from iCloud and if you also have iCloud Photo Library turned on in Photos on your Mac, they would be deleted from there as well. The design of iCloud Photo Library is to make all of your photos available on all of the devices.

If your only current objective is to delete photos from your phone without deleting them from iCloud and your Mac (assuming you are using Photos on the MacBook Pro and that it has iCloud Photo Library turned on), you could turn off iCloud Photo Library on your phone (via Settings > iCloud > Photos) and then delete photos from your phone. Note that after doing that no new photos would be automatically transferred from your phone to iCloud and to your Mac. You would have to transfer the photos manually. Also note that if you later turned it back on, all of the iCloud photos would again download to your phone and you would be back in the same storage problem. If you turn off iCloud Photo Library on your phone, and if your only objective in turning it on in the first place was to transfer photos to your Mac, then you may also want to turn it off on your Mac (after being certain that originals have downloaded to the Mac). It is hard to recommend without knowing why you turned it on in the first place. There is information about turning it off on one or all devices in Get help with your iCloud Photo Library - Apple Support

You aren't alone in the way you were thinking. Many people have thought or assumed they could store data in iCloud and completely remove it from their devices. There are 3rd party services that allow data/photos to be relocated from computers/phones and stored only on a cloud service. Apple does not currently offer that option. Using iCloud will not ensure that you don't run out of memory on your device. As I said in my initial response:

The most you can do to reduce storage required on the phone is to go to Settings > Photos & Camera and turn Optimize iPhone Storage to on.

You could make a suggestion for that option to be offered: https://www.apple.com/feedback/icloud.html