Q: how to make Bluetooth work on iphone for transfering pictures?

Are you attempting to use AirDrop to a Mac computer? Other than that, file or photo transfer via Bluetooth is not supported and even that uses wi-fi. An iPhone will not pair via Bluetooth to a computer (Mac or Windows) except for personal hotspot and then only if your cellular plan supports it. See the following for more information. https://discussions.apple.com/docs/DOC-7722

If you are attempting to use AirDrop, that does involve Bluetooth but the devices are NOT paired; Bluetooth just needs to be on and the devices in range of each other. The following may help Use AirDrop to send files from your Mac to another nearby Mac or iOS device - Apple Support