The Android app StreetComplete is an excellent start for updating OSM I found. There soon become occasions when you have to bring out the big guns and edit it using the web editor at https://www.openstreetmap.org/ , which is possible to do on a mobile phone if it has a big enough screen, but much easier on a laptop.

From my experience the best one currently is EveryDoor. But even if you just use Organic Maps, it has some basis functionality to add and edit places.

StreetComplete is also great and very beginner friendly, but it is mostly for completing missing information for existing places. However, I think quite recent addition was that now you can actually add new places. Haven't used it much though.

I haven't tried it myself, but I think https://wiki.openstreetmap.org/wiki/StreetComplete