Using RootCloak properly is easy, but remember to install Xposed first. Once you've installed Xposed, you'll be able to install RootCloak's APK. After running the module and restarting your device, you'll start to use the app correctly.
RootCloak's interface is very simple: all you need to do is choose which apps you want to "trick" so they don't know that your device is rooted. If you can't find that specific app on the list that appears by default, all you'll need to do is search for it manually, and add it to the list. It's that simple.