Open the downloaded APK. If Android asks, allow this browser to install apps, then install NCL. You can turn that permission off afterwards.

If NCL 0.3.1 or later is installed, update it without uninstalling. Only the earlier 0.2.x / 0.3.0 beta needs to be removed once.

Version 0.3.3 adds update notices. Install it once to be notified about future app releases with Update / Later options.