Q: Does the iMac 2015 have a disk drive please?

It doesn't have an optical drive, but can have an external one hooked up to it, or use another computer's.

(139553)

As Neil mentioned, iMacs (since 2012) have not included DVD drives. Apple sells their own or there are third party alternatives, all are external drives. If you have another computer that has a DVD drive and is on the same network as your iMac then you can share that drive. This feature is called Remote Disk and is explained in Apple's Use the CD or DVD drive from another computer with your Mac - Apple Support letter. It's really simple to use, my iMac is a 2011 (with a DVD drive) and my wife's is a Mac Mini without a superdrive, on the rare occasion she has a need we just use Remote Disk. This is great if your DVD needs are minor, however if you find you need a DVD drive frequently then its easiest to get an external one, don't worry they're inexpensive. If you decide to get an external one, verify the ones you are looking at support OS X. I also highly recommend OWC (www.macsales.com) because they specialize in Mac and sell a lot of alternatives, one I'm sure would fit your needs.