The image needs to be Process version 2012.
If it isn't, you'll see a lightning icon under the histogram in Develop.
Click the icon to update the process version, and Dehaze will be available.
Well, maybe not "certainly". See Per's post.
I can't remember which release had Dehaze in it
I didn't think about that, but it turns out it was released in 2015.1, and as a local adjustment in 2015.2.
Victoria Bampton's blog is a great resource for this kind of information - Blog
Thanks for reply, I am a beginner, so a lot to learn but I found this under lightroom system preferences. I have never had a prompt to update and wonder
if this is the latest version ??
Lightroom version: CC 2015 
License: Creative Cloud
Operating system: Mac OS 10
Version: 10.11 
Try Help->Updates... and see if that lets you get a later version.
You have the .0 version. Dehaze was added to the .1 version.
Try LR / Help / Updates as Hal says.
Next try CC App – right-click (or click the gear) and choose Check for Updates.
If none of that works, then you can download the .4 patcher from under the Lightroom 6 branch:
Thank you all ... finally got it through Cloud app and dehaze is there ....thanks again for taking the time to help me ...much appreciated