You don’t need import, just install plugin with npm pluginName --save. For normal typescript compilation - declare your plugin variable at top of your file. For example you need cordova
declare let cordova: any;
Plugins work only on real devices and emulators. Launch with ionic serve will cause an error. So you can try livereload on devices. Something like:
ionic emulate ios -a -b -s -c -l
And see console.log in your terminal.
Also you can try run your app on browser platform, but in my experience a half of plugin not work on it:
declare let FilePicker: any; // at the top of your file
// in your class method
FilePicker.isAvailable(function (avail) {
alert(avail ? "YES" : "NO");
});