It's a bloody disaster. I had a whole way of doing things resolved using a series of plugins and none of them are now available. I've been through every thread on here (and elsewhere) and the bottom line is that the whole thing is screwed.
I even spent hours following a process from an option under Help > Manage Extensions. Do yourself a favour, don't bother. It doesn't work, it just opens up the Extensions manager and no matter what you do, you cannot access the extensions at all.
Please click on the help tab and choose browse Add-ons.
It will open the Add on website in your default browser.
Choose Photoshop below the option All Add-ons.
Click on any add on and install it. Launch the creative cloud desktop app it would appear in it under the Home panel.
Close and re-launch Photoshop CC 2014 and click on Window tab and choose extensions.
If you still face any issue, go that specific add on web page again and choose "where to find it" and then click on download/install your add-on another way and follow the steps.