If the width of the raster corresponds with 500 m in the map image, fill in 500 in the 'Desired Raster Width' box. That will zoom the map image as much as is needed to have the raster width correspond with the map scale. Now draw your first track. Use the left mouse button to draw a track line. You can see that two GNode's have been created, with a line of track between them.
Double track Let's change the last track into double track.
Add a node to both the GNode's by right-clicking on the GNode and select Add Node. It's important where you click because that determines where the new node is added or inserted. Now you can easily draw a new track between the two new nodes. You can build additional double track from this starting point by holding down the Control button and drawing track from a multi-node GNode. Each node can have two outbound tracks on both sides.