Hello Maurutto,
Thanks for contacting me about this. Which version of the app are you using? Make sure you have the latest release, 1.6.2.
And if the app crashes at the point right after you have selected a point in the map image, and when you should find the same spot on Google Maps, then one possibility is that you have not allowed the app to access your location information. That would cause the app to crash (though the initial empty map list page should've asked you to allow access to location).
About the location access: Custom Maps does not send your location information anywhere (or any other information about you). And it obviously needs to know your location to be able to show your location on the map you create with it. During the map creation the location is only used for initially positioning the Google Map view (you really don't want to start panning and zooming every new map from a point in the Atlantic Ocean -- location 0,0 for latitude, longitude). Custom Maps assumes that the map you are creating is almost always closer to your current location than that arbitrary location in the Atlantic).
Let me know if this helps, and if it does not, I'd like to hear more details so that I can fix the app for you (and others who might have the same problem).