Seemingly unusable by design.

I have yet to be able to sucessfully use this app. From my attempts so far, it appears that you can’t use this app to access your camera without already having access to the camera, which kind of misses the point of having the app. In order to use the app, you have to have:

1) Its IP address, which appears to only be available from the advanced settings of the web page java-based app. IP addresses are not static and will change from time to time (for example when there is a power failure or I unplug the camera), so presumably I will have to use the Java app every time the IP address changes in order to use this app.
2) A user name and password. There is no clue from the app whether this is for the myDLink account, the camera’s admin account, or something new.
3) The camera’s model number, which you can get from the iOS or Java app, if you don’t happen to have the camera’s box anymore.

What you CAN’T do is get any web-based help. The support link on the App Store page leads to a 404 page, and the link in the About this app window leads to a "site under construction" page.

The iOS app has you sign in with your myDLink account and then it finds your camera for you, no other rigamarole required. I have no idea why the OS X app doesn’t do the same.
Alternatively, the app could scan the local network for cameras and present them for login access.

DeeKayUU about D-Link++ Viewer