To determine your position on the map, tap first of all on the "Map" tab and then on the circle in the lower left corner, which looks like a target. A blue point will then appear that shows and tracks your position. Tapping again on the target symbol will align the map in the direction you are facing.
Tapping anywhere on the map will switch the display to full screen mode so that you can zoom in and out. Tap again to exit this.