Hi, there is no way to insert ‘’a compass on the map’’. North is conventionally at top of map.
Windy is a weather app, not a navigation tool.
However you can get detailed information according to your flight plan with the Route planner:
... Or with the Flight planner plugin. See Windy plugins in main menu:

Route planner and Flight planner are only available via the website, not the mobile app.
(Flight planner is available on mobile via browser. Just bookmark https://www.windy.com/plugins?47.398,0.704,5)