Manual map selection and OSM

In the GUI, it is recommended to use the default toggled option and not try to select an area by hand.

If you're editing OSM at the same time, you'll want to redownload the area once your changes are done (the OSM data source is updated every minute with the user edits).

If some for reason you'd need to select an area manually, it's best to use the rectangle selection tool on the map widget and a button should appear that allows you to download the area. There will be a warning if the area is too large (which would take a long time to process). It may take a few minutes.