Watch the video or check the text version below:
MAPS.ME has maps for every country in the world, including islands. You can check how detailed they are on OpenStreetMap.org. To download maps, you can:
Zoom in the map of needed area until "Download" button appears
Tap the country or city name on the world map and then tap download icon in the pop-up window
Find a map in the list of countries (Menu → Download Maps)
Create a route and the app will prompt you to download all the necessary maps.
See also: I can't download maps. It always fails