In the mac app store version of Elements 10 there is 'get updates' link on the help menu. And when I try to do it manually from a download I get a message telling me that 'this update no applicable'.
You will need to contact Apple support. A Mac App Store purchase is a separate build of the application and cannot be updated manually.
This FAQ may help:
Once again, Apple only provides support for purchasing issues,not with using software purchased via the app store, any more than staples will give you tech support for a boxed version you buy from them:
The Mac App Store handles the download, installation, licensing, and updating of all products purchased through it. If you encounter an issue with an Adobe product during one of these four processes, visit http://www.apple.com/support.
For all other issues, including program errors and how to questions, visithttp://www.adobe.com/support.
Apple only provides support for problems with updates released via the app store and adobe has NEVER bothered to issue updates anything offered through the app store, so you can't get any help from apple for this.
It's more complicated to install ACR in the app store version. You have to do it manually. See this thread:
Well, it's not exactly wrong. It's just not correct. The thing is that the way the app store is supposed to work is that the developer releases all updates via the app store, too. For example, for Pixelmator, every time there's an update I see a notification in the app store and update it that way. And if I had a problem with that, I would first go to the app store support to see what's going on.
But since adobe has never released a single update for acr or anything else to PSE/app store, you're on your own for figuring out how to update ACR.
That is correct, all updates must come from the App Store itself. The updates for the retail versions of Photoshop Elements will not work with the App Store versions because much of the application is "protected" by the store so they cannot be modified. We are still working with Apple on this issue. For now, using DNG conversion is the only workaround.